HUMAN BONES - Skeletal system | Vertebral column | Shoulder joint

Skeletal System

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Divisions of  Skeletal System

Axial Skeleton 

■ Skull

■ Vertebral column

■ Bony thorax

Appendicular Skeleton

■ Bones of the upper limb (superior extremity) 

■ Bones of the lower limb (inferior extremity)

Articulations (Joints) 

■ Joints of the axial skeleton

■ Joints of the upper limb

■ Joints of the lower limb

Learning Outcome

Bones of the Body

1.  What is skeletal system and skeleton 

2.  What is osteology

3.  What is your idea about axial and appendicular division of the skeleton

4.  Describe vertebral column. 

5.  Write short note on: Vertebral column.

6.  How vertebral column is formed? 

7.  Name the bones of spine

8.  List the vertebrae of the human body 

9.  Draw and label the parts of a typical vertebra

10. Describe a typical vertebra with diagram

11. Write done the function of a typical thoracic vertebra

12. Name the bones of thorax 

13. Explain sternum

14. Classify rib

15. Narrate the characteristics of a typical rib with diagram 

16. Describe the function of a typical rib What i

17. What is thoracic cage?

18. Write short note on: Thoracic cage 

19. Name bones of thoracic cage

20. Name the bones of upper limb

21. Describe humerus with diagram.

22. Draw, label and describe clavicle 

23. Describe humerus with diagram

24. Describe the upper part of the humerus 

25. Name the bones of the lower limb (lower extremity)

26. What are the difference between male and female pelvis 

27. Describe femur in short / Describe femur with diagram

THE SKELETAL SYSTEM

Questions

➤ What is skeletal system and skeleton? / What is osteology?

■ Skeletal system:

The skeletal system is the internal framework of the human body composed of bones. 

■ Skeleton:

The bony framework of the body supporting the soft tissues and protecting the internal organs is known as skeleton.

■ Osteology: Osteolog is the study of structure and function of the bones. 

         There is also a term musculoskeletal system, which is an integrated system consisting of the bones, muscles and joints that together move the body.

Functions of the skeletal system

1. Protection: Delicate tissues and organs are often surrounded by the skeletal frame. 

2. Blood cell production: Red bone marrow, which fills the cavities of many bones,

produces RBC and other blood cells.

■ Bony Skeleton and Its Divisions

Definition: The skeleton is the bony framework of the body providing support and protection for some of the soft organs, acting as levers in movement and providing surfaces for the attachment of the skeletal muscles.

Number of bones forming adult skeleton: The adult skeleton is made up of 206 named bones.

Divisions of skeleton

The skeleton is divided into two main divisions: axial skeleton and appendicular skeleton.

Axial skeleton:

It consists of the bones along the longitudinal axis of the body that support the head, neck and trunk.

The bones are: skull, hyoid, vertebral column (including the sacrum), ribs, and sternum.

Appendicular skeleton:

It consists of the bones of the upper and lower limbs, and of the pectoral (shoulder) girdle and pelvic girdle

•  Upper limb (or extremity): Humerus, radius, ulna, carpal bones, metacarpals, phalanges. 

•  Pectoral (shoulder) girdle: Clavicle, scapula.

•  Lower limb (or extremity): femur, tibia, fibula, tarsal bones, metatarsals, phalanges.

THE AXIAL SKELETON

Skull

The skeleton of the head and face together is called the skull.

• Cranium (calvaria)-which consists of eight fused bones enclosing the brain. 

• Facial skeleton- which consists of 13 fused bones and the movable mandible of the lower jaw.

General Features of skull

•  The skull forms the large cranial cavity; divided into anterior, middle, and posterior cranial fossae. It also forms several smaller cavities, such as the nasal cavity and orbits.

•  Certain skull bones contain air cavities called paranasal sinuses.

•  Immovable joints called sutures fuse most of the skull bones together. These sutures can be seen on the outer surface of the skull 

Some skull sutures are: Coronal suture, sagittal suture, lambdoid suture, parietomastoid suture etc.

•  The skull has many surface markings, such as foramina and fissures through which blood vessels and nerves pass.

•  The outer surfaces of cranial bones provide large areas of attachment for muscles that moves various parts of the head.

CRANIAL BONES

Frontal Bone

The frontal bone forms the forehead (anterior part of the cranium), the roofs of the orbit, and most of the anterior part of floor of the skull.

Parts:

• Squamous part (vertical part). 

• Orbital plates, one on each side (horizontal parts)

• Nasal part

Important Features:

• Supraorbital foramen (notch) is an opening along the supraorbital margin, which allows the small supraorbital vessels and nerve passing to and from the forehead. 

• Frontal bone contains frontal sinuses that communicate with the nasal cavity.

Parietal Bones

The two parietal bones form a large part of the roof and sides of the cranium. On both sides of the skull, parietal bones are posterior to the frontal bone. 

Important Features: 

• Shape-Each parietal bone is quadrilateral.

• The external surface is convex, has two well-marked ridges,called temporal lines. 

• The internal surface is concave and is grooved by the brain and blood vessels.

Articulations: 

• Inferiorly, they articulate with the temporal bones at the squamous suture.

Occipital Bone

The occipital bone forms the back of the cranium and posterior part of the base of the skull. 

Parts:

The occipital bone consists of three parts:

• Squamous part 

• Condylar parts

• Basilar part

Important Features:

• The occipital bone surrounds an opening, called foramen magnum, through which is transmitted the lower part of the brain stem.

• On either side of the foramen magnum are the occipital condyles which articulate with the atlas (1st cervical vertebra) at the atlanto-occipital joint.

• Its internal surface is deeply concave and the concavity is occupied by the occipital lobes of the cerebrum and by cerebellum.

These are areas of muscle attachment.

Temporal Bones

The two temporal bones are present on each side of the cranium, below the parietal bones. They form the inferior lateral aspects of the cranium and part of the floor of the skull.

Parts:

The temporal bone consists of three parts- 

(i)   Squamous part 

(ii)  Tympanic part 

(iii) Petromastoid part

Important Features:

• The squamous part is the thin fan-shaped area which forms part of the lateral wall of the cranium.

• The tympanic part of the temporal bone displays the external acoustic meatus (ear canal) and the styloid process.

The mandibular fossa lies immediately anterior to the tympanic plate. 

• The mastoid part of the temporal bone contains mastoid process.

• The petrous part of the temporal bone contains the middle and inner ear structures. 

• The mastoid process and the styloid process serve as a point of attachment for muscle and ligaments of the neck and tongue.

• Between the styloid process and the mastoid process is the stylomastoid foramen, through which the facial nerve (VII) and stylomastoid artery pass.

Sphenoid Bone

This bone is butterfly-shaped.

Parts:

The sphenoid bone consists of-

• Body

• Two lesser wings 

• Two greater wings

• Two pterygoid processes

Important Features of Sphenoid Bone:

• The body of the bone is cube-shaped and contains the sphenoid sinuses.

• On the superior surface in the middle of the bone is a bony depression, the hypophysis fossa (sella turcica) in which the "pituitary gland" rests. 

• Optic foramen is present in the lesser wing, through which optic nerve and ophthal

artery pass.

• Three foramina are present on the upper surface of the sphenoid bone: 

    Foramen rotundum (to transmit maxillary nerve)

    Foramen ovale (to transmit mandibular nerve)

    Foramen spinosum (to transmit middle meningeal vessels).

Articulations:

• It articulates anteriorly with the frontal bone,

• Laterally with the temporal bones, and 

• Posteriorly with the occipital bone. .

Ethmoid Bone

The delicate ethmoid bone occupies the superior part of the nasal cavity. 

It helps to form the orbital cavity, the nasal septum and the lateral walls of the nasal cavity.

Important Features:

• The perpendicular plate of the ethmoid bone forms upper part of the nasal septum.

• The cribriform plate of the ethmoid bone forms the roof of the nasal cavities. The cribriform plate contains perforations for the passage of the olfactory nerves.

• Bony projections called the superior and middle nasal conchae (turbinates) extend into the nasal cavity.

Principal sutures of the skull

Principal sutures of the skull are -

• Coronal suture: Articulation between frontal bone and two parietal bones anteriorly.

• Sagittal suture: Articulation between two parietal bones superiorly at the middle of the skull. 

• Lambdoid suture: Articulation between occipital bone and parietal bones posteriorly. 

• Squamous suture: Articulation between a parietal bone and a temporal bone on the lateral aspect of the skull.

Fontanels of the skull

There are six large membranous areas on the fetal skull, called fontanels, that permit the skull to undergo changes in shape (molding) during childbirth (delivery). 

■  Anterior fontanel is the largest fontanel. It is somewhat diamond-shaped membrane that lies on the median line at the junction of the frontal and parietal bones. 

■  Posterior fontanel, smaller one that lies on the median line at the junction of the parietal and occipital bones. 

■  Ossification of the fontanels is normally completed by 20 to 24 months of age.

Paranasal Sinuses

Some of the bones of the skull contain cavities, called paranasal sinuses that have passageways leading into the nasal cavity.

The paranasal sinuses are named after the bones in which they are situated, such as: 

• Frontal sinus (in frontal bone)

• Maxillary sinuses (in maxillae)

• Sphenoidal sinus (in sphenoid bone) 

• Ethmoid air cells (in ethmoid bone)

Functions of Paranasal sinuses:

1. Reduce the weight of the skull 

2. Add resonance to the voice

FACIAL BONES

Maxilla (upper jaw bone)

Two maxillae are joined by a suture on the median line. 

They form the upper jaw; the anterior part of the roof of the mouth, or hard palate; parts of the orbital and nasal cavities.

Parts:

Each maxilla consists of-

• The body

• The frontal process

• The alveolar process.

• The zygomatic processes. 

• The palatine process

Important Features:

• The body is pyramidal in shape and contains the large maxillary sinus.

• The alveolar process projects downwards from the body of the maxilla to form sockets

for the upper teeth.

• Foramina present in the maxilla:

1. Infraorbital foramen. It is an opening in the maxilla below the orbit. It transmits-

 (i) Infraorbital nerve and blood vessels, and

 (ii) A branch of the maxillary division of the trigeminal (V) nerve. 

2. Incisive foramen. It lies just posterior to the incisor teeth. It transmits branches of the - 

 (i) Greater palatine blood vessels.

 (ii) Nasopalatine nerve.

Articulations of the Maxilla

It articulates -

• Superiorly, with the nasal, frontal and lacrimal bones; 

• Medially, with the ethmoid, inferior nasal concha, vomer, palatine and opposite maxilla;

• Laterally, with the zygomatic bone.

Mandible

The mandible is the bone of lower jaw, the only movable bone of the skull.

Parts:

mandible consists of-

• The body, which lodges the teeth

• Two rami, which project upwards from the body. They provide attachment to the muscles of mastication.

Body

It is horseshoe-shaped. 

Each half of the body of mandible has -

• Two surfaces: Outer and inner 

• Two borders: Upper and lower.

Ramus

It is quadrilateral in shape and has - 

• Two surfaces: Lateral and medial

• Two processes: Coronoid and condyloid.

Foramina

• Mental foramen - lies approximately inferior to the second premolar tooth.

It transmits the mental nerve and vessels

Structures related to the mandible

1. Salivary glands: Parotid, submandibular and sublingual.

2. Lymph nodes: Parotid, submandibular and submental.

3. Arteries: Maxillary, superficial temporal, messeteric, inferior alveolar mylohyoid, mental and facial.

4. Nerves: Lingual, auriculotemporal masseteric, inferior alveolar, mylohyoid and mental.

Zygomatic Bone

On each side of the face are two zygomatic bones. 

They form the prominences of the cheeks and the inferior and lateral walls of the orbital cavities

Nasal Bones

Lacrimal Bones

The two small, thin lacrimal bones are posterior and lateral to the nasal bones. 

Each lacrimal bone is pierced by a foramen for the passage of the nasolacrimal duct through which tears flow from the eye to the nasal cavity.

Palatine Bones

These are two small L-shaped bones.

Parts

Each palatine bone consists of-

• vertical plate

• horizontal plate 

• pyramidal process

• sphenoidal process

• orbital process

Important Features:

•The horizontal plates of two bones unite to form the posterior third of the hard palate - the "roof of the mouth." 

• The vertical parts project upwards to form part of the lateral walls of the nasal cavity.

Inferior Turbinates (Conchae)

Vomer

The vomer is a thin flat bone. It extends upwards from the middle of the hard palate to form most of the inferior part of the nasal septum.

ORBITS

Definition: The orbit is a pyramid-shaped structure formed by seven bones of the skull, which contains the eyeball and associated structures. 

The bones contribute to the orbit are: frontal, sphenoid, ethomoid, palatine, zygomatic, lacrimal and maxilla.

Four regions of orbit:

• Roof

• Lateral wall

• Floor, and

• Medial wall.

Openings of orbit:

(1) Supraorbital foramen - on the medial side of the supraorbital margin of the frontal bone.

Contents of orbit:

1. Eyeball - It occupies anterior one-third of the orbit.

2. Fascia - Orbital and bulbar.

3. Muscles - Extraocular and intraocular. 

4. Nerves - Optic, oculomotor, trochlear and abducent; branches of ophthalmic and maxillary nerves, and sympathetic nerves.

VERTEBRAL COLUMN

Definition

Vertebral column is the central bony axis of the body, a flexible curved structure that extend downwards from the occipital bone of the skull to the coccyx.

The vertebral column is also called the spine or backbone. 

Formation

The vertebral column composed of 26 bones and connective tissue:

• 24 separate vertebrae (singular: vertebra)

• Sacrum

• Соссух

Sacrum is formed from five fused vertebrae and coccyx is formed from 3-5 small fused vertebrae. The 24 separate vertebrae can be divided into three groups - 

• Cervical-7 

• Thoracic - 12 

• Lumbar -5

Length

The total length of the vertebral column is about 70 cm in male and 60 cm in female.

Divisons:

The vertebral column has five major divisions (or regions).

• Cervical spine - formed by first seven vertebrae in the neck. 

• Thoracic spine - formed by the next twelve vertebrae in the thorax.

• Lumbar spine - formed by the next five vertebrae supporting the lower back. 

• Sacrum - inferior to the lumbar vertebrae, which articulates with the hip bones of the pelvis

• Coccyx - is the terminus of the vertebral column.

Features of the Vertebral Column

Each disc consists of an outer rim of fibrocartilage called annulus fibrosis and a central core of soft gelatinous material called nucleus pulposus. 

The discs have a shock-absorbing function and the cartilaginous joints they form contribute to the flexibility of the vertebral column as a whole.

■ Intervertebral foramina :

Throughout the length of the vertebral column there is an intervertebral foramen on each side between every pair of vertebrae, 

Through the intervertebral foramina the following structures pass -

• Spinal nerves

• Blood vessels

• Lymph vessels

■ Curves of the vertebral column:

• Thoracic curve 

• Pelvic curve } Convex posteriorly, primary curvature is present since birth.

• Cervical curve 

• Lumbar curve }Concave posteriorly, develop after birth and are called secondary curvature

Ligaments of the Vertebral Column

(i)   Transverse ligament - maintains the odontoid process of the axis in the correct position in relation to the axis.

(ii)  Anterior longitudinal ligament - extends the whole length of the vertebral column anterior to the vertebral bodies.

(iii) Posterior longitudinal ligament - extends the whole length of the vertebral column within the vertebral canal.

(iv)  Ligamentum nuchae and supraspinous ligament - connect the spinous processes of the vertebrae from the occiput to the sacrum.

Movements of the Vertebral Column

The movements of the vertebral column as a whole are quite extensive and include - 

• Flexion (bending forward)

• Extension (bending backward) 

• Lateral flexion (bending to the side)

• Rotation

Deformities of the Vertebral Column

In some conditions the vertebral column becomes abnormally curve. These abnormal curvatures are called deformities. These are -

1. Kyphosis: The forward bending of the vertebral column, typically seen in the thoracic region in older persons.

2. Lordosis: The backward bending of the vertebral column, occurs most commonly in the lumber region.

3. Scoliosis: The lateral bending of the vertebral column, occurs most often in the thoracic region.

Functions of the Vertebral Column

These the following -

• It supports the skull.

• It forms the axis of the trunk, giving attachment to the ribs, shoulder girdle and and upper limbs the pelvic girdle and lower limbs. upper limbs.

THE VERTEBRA

In adult human body, there are 26 vertebrae including sacrum and coccyx, forming the vertebral column. 

The vertebrae are named according to the region where they arranged one by one from above to below.

Question

➤ List the vertebrae of the human body

Functions of the Vertebrae

1. Protect the spinal cord

2. Provide support to the body in respect to flexibility, stability and power 

3. Serve as a place in which the pectoral and pelvic girdles as well as many muscles attach.

Question

➤ Down the function of a typical thoracic vertebra.

Functions of typical thoracic vertebra

1) Gives protection to the spinal cord. 

2) Serves as the attachment points for the rib cage which protects the vital organs of the chest, e.g., lungs, heart and great vessels. 

3)Helps the body stand upright.

TYPICAL VERTEBRA

➤ Draw and label the different parts of a typical vertebra.

➤ Describe a typical vertebra with diagram.

Parts and characteristics of typical vertebra

A typical vertebra consists of:

1. The body (anterior part, situated anteriorly), 

2. The vertebral arch (posterior part, lies behind the body).

The two parts together enclose the vertebral foramen, which contains the spinal cord.

Body

The more massive, weight-bearing anterior portion of a vertebra, shaped like a short cylinder is called the body.

Vertebral arch 

Sven processes project from the vertebral arch - 

      Two transverse processes

      Twe superior articular processes 

      Two innor articular processes

      One spinous process

• Pedicles: Two short bony plates that connect the vertebral arch to the body. The pedicles are directed backwards and laterally 

• Laminae: Two flat plates of bone that extend from each pedicle to meet in the midline

• Transverse process: A lateral prominence, projecting from the regions where the pedicle meets the lamina. Two in number.

• Spinous process: Where the two laminae meet at the back is a process called the spinous process in projects posteriorly and inferiorly. It provides site for attachment of muscles and ligaments

• Articular processes: The vertebral arch has four articular processes, two superior and two inferior.

The superior articular processes articulate with the vertebra above and the inferior articular processes with the vertebra below.

Vertebral foramen

There is a large vertebral foramen bounded anteriorly by the posterior aspect of the body, and posterioly by the vertebral arch.

Dinging features of region-specific typical vertebrae

VERTEBRAE - CHARACTERISTIC FEATURES

Cervical - Presence of foramen transversarium in the transverse process 

Thoracic - Presence of costal facets on the body and transverse process for articulation with the ribs

Lumber - The large size of the body, absence of foramen transversarium and costal facets

CERVICAL VERTEBRAE

Number/Typical/Atypical:

There are 7 cervical vertebrae, out of which -

• The first two (axis and atlas) and 7th are atypical, 

• The rest 3rd to 6th cervical vertebrae are typical.

Identification:

These are the smallest vertebrae. The transverse processes have a foramen, named foramen transversarium, through which a vertebral artery passes upwards to the brain.

Atlas (First cervical vertebra, C₁)

• It is the vertebra on which the skull rests.

Axis (Second cervical vertebra, C₂) 

• The second cervical vertebrae is called axis, which lies below the atlas. 

• It has a small body with a small superior projection called the odontoid process (also called the dens, meaning tooth).

7th Cervical vertebra (Vertebra prominens, C7)

THORACIC VERTEBRAE

12 thoracic vertebrae lie in the thoracic region of the body.

Typical & Atypical Thoracic Vertebrae 

• 2nd to 8th thoracic vertebrae present common features and are called typical thoracic vertebrae.

• 1st, 9th, 10th, 11th and 12th thoracic vertebrae present special features and are called atypical vertebrae.

Identification of Thoracic Vertebrae

(1) The thoracic vertebrae are larger than the cervical vertebrae, but smaller than the lumbar vertebrae

(2) The bodies and transverse processes have costal facets for articulation with the ribs.

(3) The body is heart-shaped. 

(4) Circular vertebral foramen.

LUMBAR VERTEBRAE

Number: There are five lumbar vertebrae in the region of the loin.

Typical & Atypical Lumbar Vertebrae

• From 1st to 4th lumbar vertebrae are typical

• Only the 5th lumbar vertebra has some special features, and is atypical.

Identification of Lumbar Vertebrae

(1) Lumbar vertebrae are the largest of the vertebrae.

(2) Absence of costal facet and foramen transversarium.

(3) Spinous process is quadrangular and horizontal, it gives muscle attachment.

SACRUM

• The upper part, or base of sacrum articulates above with the fifth lumbar vertebra.

BONES OF THORAX AND THORACIC CAGE

Question

➤ Name the bones of thorax.

Bones of thorax

The thorax or thoracic wall consists of:

• Sternum (anteriorly)

• 12 thoracic vertebrae (posteriorly)

STERNUM 

Question

Explain stemum.

Definition:

The sternum is a long flat bone that can be felt just under the skin in the middle of the front of the chest.

Parts:

The sternum consists of three parts (from above to below) -

1. Manubrium

2. Body

3. Xiphisternum (Xiphoid process)

Manubrium

It is the uppermost broad, triangular part. It articulates with the clavicles at the sternoclavicular joints, It also articulates with the first two pairs of ribs.

Body

The long and narrow middle portion of sternum is the body. It provides sites of articulation for the ribs on its lateral sides.

Xiphisternum (Xiphoid process)

It forms the lower end of the sternum.

Importance of sternum

• The sternum forms the anterior portion of the cage, and thus helps to protect the lungs, heart and major blood vessels from physical trauma.

• Its upper end supports the clavicles, and provides articulation for the first 7 pairs of ribs.

• Clinical importance: Sternal puncture is done in this bone to aspirate bone marrow for study. This is a diagnostic test for some diseases, e.g., aplastic anaemia, leukemia, kala-azar etc.

RIBS

Definition: The ribs are long, slender, elastic bony arches which form a large part of skeleton of the thorax.

Question

➤ Classily rib.

Classification of Ribs

1. According to features:

(i) Typical ribs - 3rd to 9th ribs. 

(ii) Atypical ribs - 1st, 2nd, 10th, 11th and 12th ribs.

2. According to relation with the sternum:

(i) True ribs - 1st to 7th ribs. i.e. upper 7 ribs are connected to the sternum by costal cartilages. 

(ii) False ribs - 8th to 12th ribs, i.e. lower 5 ribs do not articulate with the sternum anteriorly.

3. According to articulation:

(i)  Vertebrosternal ribs - 1st to 7th ribs.

(ii) Vertebrochondral ribs - 8th to 10th ribs. 

(ii) Vertebral (floating) ribs - 11th and 12th ribs

  • Vertebral or floating ribs articulate posteriorly with vertebrae but their anterior ends do not connect either with other ribs or with the sternum.

Typical Ribs

Question

➤ Narrate the characteristics of a typical rib with diagram.

Characteristic features (Identification) of a typical rib

1. Its shaft is curved with an external convexity. 

2. It is angulated. The angle lies 5-6 cm from the tubercle.

3. It is twisted, so that two ends of the rib cannot touch the same horizontal plane.

4. Costal groove is present in the internal surface along the inferior border of the shaft.

Features of Typical Ribs

Parts:

Each rib has three parts -

• Two ends - anterior and posterior

• Shaft

The anterior end has a concave depression which joins the corresponding costal cartilage.

The posterior end has head, neck and tubercle. 

The shaft or body is the longest part that extends between anterior and posterior ends. The shaft has two surfaces (outer and inner), two borders (upper and lower) and an angle.

The inner surface is marked along the lower border by a groove, the costal groove. This

groove lodges the contents of the intercostal space, such as -

(i) Intercostal vein

(ii) Intercostal artery

(iii) Intercostal nerve

Question

➤ Describe the function of a typical rib.

(1) Takes part in the formation of rib cage, which is a flexible structure that can change its shape and size during breathing. The intercostal muscles, which are needed for breathing, are attached to the ribs. In this way a typical rib helps in breathing.

(2) Protection: Gives protection to vital organs of the chest e.g. lungs, heart, great vessels etc.

THORACIC CAGE

Questions

➤ Write short note on: Thoracic cage.

➤ What is thoracic cage? Write down the boundary of thoracic cage.

Formation

The thoracic cage is formed by the sternum anteriorly, twelve pairs of ribs at the lateral sides, and the twelve thoracic vertebrae posteriorly.

The costal cartilages and intervertebral discs also take part in the formation of the rib cage.

Boundaries

The boundaries of the thoracic cage are:

• In front-The sternum and costal cartilages

• Behind-The twelve thoracic vertebrae with their intervertebral discs

• Laterally (at the sides)-Ribs and intercostal muscles

• Below-The diaphragm

• Above-The root of the neck

Functions of thoracic cage

1. It supports the pectoral girdle and upper limbs.

2. It protects and supports the thoracic and upper abdominal viscera. 

5. It provides an extensive surface area for muscle attachment.

4. It plays a major role in respiration.

It uses intercostal muscles to lift and depress the thorax during breathing

Question

➤ Name the bones of upper limb.

Bones of the upper limb (Superior extremity) 

Each upper limb has 32 bones. So, the total number of upper limb bones are 64, out of these 10 shoulder and arm, 16 wrist and 38 hand bones.

■ The 10 shoulder and arm bones: clavicle, scapula, humerus, radius, and ulna (on each side). 

■  The 16 wrist bones: scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate (on each side). 

■ The 38 hand bones: 10 metacarpal bones and 28 phalanges.

Shoulder girdle

It is composed of two scapulae (singular: scapula) and two clavicles.

SCAPULA

The scapula is a flat triangular-shaped bone located on the upper part of the posterolateral aspect of the thorax, between second to seventh ribs.

Parts

The scapula consists of four parts: body and three processes-spinous, acromion, and coracoid.

Body:

Triangular, thin and transparent. It presents the following features -

• Two surfaces: costal (anterior) and dorsal (posterior).

• Three borders: superior, medial and lateral 

• Three angles: superior, inferior and lateral. 

• Three fossae: infraspinous, supraspinous and subscapular

Processes:

• Acromion process is an anterolateral projection of the spine, which can be felt as the highest point of the shoulder. It forms a joint with the clavicle, the acromioclavicular joint

• Coracoid process is a hook-like projection from the upper border of the bone. 

It gives attachment to muscles that move the shoulder joint.

Glenoid cavity:

It is a shallow depression with articular surface at the lateral angle. 

The head of the humerus articulates with the glenoid cavity and forms the shoulder joint.

CLAVICLE (collar bone)

Question

➤ Draw, label and describe clavicle.

Definition

The clavicle is an S-shaped long bone. It is located horizontally on the anterior aspect of body at the junction of the root of the and trunk

Parts: The clavicle consists of a shaft and two ends - sternal end and acromial end.

• The medial two-thirds of the shaft of clavicle is convex anteriorly, its lateral third is concave anteriorly.

Peculiarities of clavicle

The peculiar feature of the clavicle are:

1. It has no medullary cavity

2. It is subcutaneous throughout its extent

3. It is the first bone to start ossifying (between the 5th and 6th week of intrauterine life) and last bone to complete the ossification.

Functions of clavicle

• It acts as a strut for holding the upper limb far from the trunk so that the upper limb can move freely.

HUMERUS

Questions

➤ Describe humerus./ Describe humerus with diagram./ Describe the part of the humerus.

Parts

The humerus consists of-

• shaft

• two ends: upper and lower.

Important Features

1. Upper end presents the following features:

(i) Head

(ii) Neck

(iii) Greater tubercle

(iv) Lesser tubercle 

(v) Bicipital groove or intertubercular sulcus

• Head of the humerus is smooth, hemispherical which fits into the glenoid cavity of the scapula, forming the shoulder joint.

• The anatomical neck is a slight constriction immediately inferior to the head. 

• Greater tubercle is lateral to the head of the humerus. It bears three areas for attachment of muscles: supraspinatus, infraspinatus and teres minor.

• It is also called the intertubercular sulcus, through which passes the tendon of the biceps brachii muscle.

2. Shaft of the humerus is the long, cylindrical portion. The shaft has three borders: anterior, medial, lateral

• Along its lateral mid region is a prominent ridge called the deltoid tubersosity. Deltoid muscle is attached to this roughened site. 

• In the middle of the lateral border is a depression, the radial or spiral groove along

which passes the radial nerve.

3. Lower end of the homerus is expanded side by side, which presents: 

• Capitulum, the lateral rounded articular surface that articulates with the head of humerus.

• Trochlea, the pully-like medial surface that articulates with the ulna. 

• On either side, lateral and medial epicondyles are present.

• Cornoid fossa and radial fossa are two depressions on the anterior aspect of the humerus, above the trochlea and the capitulum respectively. 

On flexion of the forearm, these fossae accommodate the coronoid process and the head of the radius respectively 

• Olecranon fossa is a deep depression of the posterior aspect of the humerus. 

On extension of the forearm, this fossa accommodates the olecranon of the ulna.

RADIUS

It is a long bone.

Parts

The radius consists of three parts: upper end, shaft and lower end.

■ Upper (or proximal) end presents head, neck and radial tuberosity.

The radial tuberosity is present below the neck, where the biceps brachii muscle is attached

■ Shaft is narrow at the upper part and much broader at the lower part. The shaft has 3 borders: anterior, posterior and interosseous; and 3 surfaces: anterior, posterior and lateral.

The lateral surface is marked by an oval "pronator tubercle," where the pronator teres muscle is attached.

■ Lower (or distal) end is the widest part having five surfaces. 

The lateral surface projects medially as the styloid process.

The distal end presents two facets for articulation with two carpal bones (scaphoid and lunate).

ULNA 

It is a long bone.

Parts 

The ulna consists of three parts: upper end, shaft and lower end.

■ Upper end (Proximal end) 

The upper end is expanded and hook-like. It is much larger than the upper end of the radius. 

The upper end has - 

         Two processes: olecranon process and coronoid process

         Two notches: trochlear notch and radial notch

         Tuberosity of ulna.

■ Shaft

The shaft of the ulna is broad proximally and narrow distally to form a small distal head. It has three borders: anterior, posterior and interosseous; and three surfaces: anterior, posterior, and medial.

■ Lower end (Distal end)

NOTE 

• The two bones-radius and ulna are parallel in anatomical position.

BONES OF THE HAND

The 27 bones of the hand are grouped into:

• Carpal bones-8

• Metacarpal bones-5

• Phalanges-14

CARPAL BONES (Carpus)

The carpal bones are arranged in two transverse rows of bones each:

• Proximal row: scaphoid, lunate, triquetral, pisiform (from lateral to medial).

• Distal row: Trapezium, trapezoid, capitate, hamate (from lateral to medial).

METACARPAL BONES

PHALANGES (Finger Bones) 

A single finger bone is called the phalanx. 

The phalanges articulate with the metacarpal bones and with each other, by hinge joints.

Pelvic Girdle

■  Formation: The pelvic girdle is formed by the two hip bones united anteriorly by the symphysis pubis. It is attached posteriorly to the sacrum of the vertebral column sacroiliac joints.

■ Function: The pelvic girdle attaches the lower limb to the axial skeleton, transmitting the weight of the upper body to the lower limbs. 

The pelvic girdle also supports and protects the visceral organs of the pelvis, includings the urinary bladder, the reproductive organs, and in pregnant woman, the developing fetus.

HIP BONE (Innominate Bone)

The hip bone is a large, flattened, irregular bone.

Parts: Each hip bone consists of three parts -

(1) ilium (2) pubis (3) ischium.

In adults, these parts meet at the acetabulum, a large, deep cup-shaped cavity on the lateral surface of the bone.

Ilium

The ilium is the upper expanded plate-like part of the hip bone. It presents the following features:

■ Iliac crest - The broad, convex ridge forming the upper limit of the ilium. Its anterior curve is called the anterior superior iliac spine and the projected posterior end is called the posterior superior iliac spine.

■ Borders - The three borders are anterior, posterior and medial.

■ Surfaces - The three surfaces are gluteal surface, iliac fossa and sacropelvic surface.

     •  This surface provides origin to gluteal muscles (gluteal maximus, medius and minimus).

     • The iliac fossa is a large, shallow, concave surface of the ilium. It forms the posterolater wall of the greater (or true) pelvis. This surface gives attachment to iliacus muscle. 

     • The sacropelvic surface is the posteroinferior part of the inner surface of the ilium. It consists of three parts: iliac tuberosity, auricular surface and pelvic surface.This surface also provides attachment to muscles and ligaments.

Pubis

The pubis is the anterior and inferior part of the hip bone. It articulates with the pubis of the opposite hip bone, forming the joint called symphysis pubis. 

The pubis consists of three parts: body, superior ramus and inferior ramus.

Ischium

The ishcium is the posterior and inferior part of the ilium.

The ischium consists of two parts: body and ramus.

• The lower end of the body forms rough inferior projection, ischial tuberosity. 

• The posterior border of the body presents ischial spine.

• The ramus of the ishcium arises from the lower part of the body and runs upward, forward and medially to join the inferior pubic ramus.

Acetabulum

• It is a large cup-shaped cavity on the outer surface of the middle constricted part of the hip bone. 

(i) Pubis (forms the anterior one-fifth) 

(ii) Ischium (forms the posterior two fifths) 

(iii) Ilium (forms the superior two fifths)

• The acetabulum receives the head of the femur to form the hip joint.

Obturator foramen

• It is large and oval in male while triangular and smaller in female. 

• Obturator canal (which is formed in the obturator foramen) transmits obturator nerve and vessels.

BONY PELVIS

Definition:

The pelvis is articulated bony structure for the pelvic cavity.

Formation:

The bony pelvis is formed by two hip bones (on either side), the sacrum and coccyx(behind). These bones are articulated by four joints - 

• Symphysis pubis

• Two sacroiliac joints, and

• Sacrococcygeal joint

Component parts:

1. Pelvic inlet (superior pelvic aperture) or brim: It completely ringed by the bones. 

2. Pelvic outlet (inferior pelvic aperture): It is formed by the bones and ligaments.

Divisions/Parts:

The pelvis is divided into two parts: Greater pelvis (or false pelvis) and lesser pelvis (or true pelvis) by the pelvic inlet or superior pelvic aperture.

■ Greater pelvis (False pelvis)

• It is the part of pelvis above the pelvic brim and is formed by two iliac fossae. 

• It is generally considered as a part of the abdomen (the lower part of abdominal cavity). 

• It contains sigmoid colon and coils of ilium.

■ Lesser pelvis (True pelvis)

• It is the part of pelvis below the pelvic inlet or brim. 

• It is enclosed by sacrum and lower parts of the two hip bones (below the pelvic inlet)

Questions

▸ Describe femur in short. / Describe femur with diagram.

FEMUR

The femur, the single bone of the thigh, is the longest, largest, and strongest bone in the body.

Parts of Femur

The femur consists of three parts-

1. upper end

2. shaft

3. lower end

■ The upper end consists of:

• Head

• Neck

• Greater trochanter 

• Lesser trochanter

■ The lower end is formed by two bony prominences:

• Medial condyle

• Lateral condyle

Upper end

• Head forms about two-third of a sphere and articulates with the acetabulum of the hip bone to form the hip joint. There is a small central pit called the fovea capitis on the head. 

• The constricted neck of the femur supports the head of the femur, and is a common site for fracture in the elderly.

• At the junction of the shaft and neck are the greater trochanter and lesser trochanter. The two trochanters are connected by the intertrochanteric line anteriorly and by the prominent intertrochanteric crest posteriorly. 

These trochanters serve as sites of attachment for thigh ad buttock muscles.

Shaft 

• The shaft of the middle third of the femur presents three surfaces: anterior, medial

lateral, three borders: medial, lateral and posterior. 

• It presents medial (inner) and lateral (outer) lips and an intervening area.

• The lateral lip become continuous with the lateral supracondylar line.

Lower end (Distal end)

• The lower end of the femur has two articular lateral and medial epicondyles, which articulate with the tibia. The depression between the condyles on the anterior surface called the patellar surface. This surface articulates with the patella. 

PATELLA (Knee cap)

Characteristics:

• It is developed in the tendon of quadriceps femoris muscle.

• It is associated with knee joint.

Features:

The patella presents following feat

Apex

Three borders - superior, medial and lateral. 

Two surfaces - anterior and poster

Functions:

• To increase the leverage of the quadriceps femoris muscle as it contracts to straighten (extend) the leg.

TIBIA (Shin Bone) 

It is much more massive than the fibula.

Parts

The tibia consists of-

upper end 

shaft

lower end

Upper end:

The upper end of the tibia is expanded. It presents two prominent condyles: medial condyle and lateral cndyle; intercondylar area and tibial tuberosity

• It presents four surfaces - superior, posterior, anterior and medial. The lateral condyle also presents four surfaces - superior, posterior, anterior and lateral.

• Lateral condyle has on its lateral aspect a small circular smooth articular facet for the head of fibula.

• The intercondylar area lies between the articular surfaces of the medial and lateral condyles. 

• Tibial tuberosity is a rough triangular area on the anterior aspect of the upper end of the tibia below the site of junction between the two codyles.

It is the site for attachment of the patellar ligament.

Shaft:

The shaft of the tibia has three borders: anterior, interosseous and medial; and three surfaces posterior, medial and lateral. 

The posterior surface of the shaft shows an oblique line, extending from the fibular facet to the junction of the upper and middle thirds of the medial border, called soleal line.

The shaft provides attachment to many muscles and fascia.

Lower end:

The lower end of the tibia shaped like a rectangular box with a bony prominence on the medial side, called medial malleolus.

It presents five surfaces: anterior, posterior, lateral, medial, and inferior. 

The lateral surface shows a deep triangular notch called the fibular notch, for articulation with the distal head of the fibula.

FIBULA 

It is more important for muscle attachment. It does not bear weight.

Parts

The fibula consists of-

• Head (upper end)

• Shaft, and

• Lower end.

Upper and (Head)

• A globe-shaped expansion at the upper end of the fibula is the head. It bears an articular surface for articulation with the lateral condyle of the tibia.

• A styloid process is an upward projection posterolateral to the articular facet.

• Neck is a constriction below the head, connecting it with the shaft.

Shaft

It presents three borders: anterior, posterior, and intenseous; and three surfaces: medial, lateral, and posterior. 

The three surfaces of the fibula are associated with the three muscular compartments of the leg.

Lower end 

On the medial surface of the lateral malleolus is a triangular articular facet for the articulation with the talus. 

Pasteroinferior to the articular facet for talus is a pit or fossa, called the malleolar fossa.

Functions of fibula

• Provides attachments for muscles.

• Its lower end along with the lower end of the tibia forms a socket (fibiofibular mortise), to hold the talus in place.

SKELETON OF THE FOOT

The skeleton of the foot consists of the following (from posterior to anterior):

• Tarsals (7) 

• Metatarsals (5)

• Phalanges (14)

TARSAL BONES

(i)   Proximal row: Talus and calcaneus

(ii)  Middle row: Navicular

(iii) Distal row: Three cuneiforms (medial, intermediate, and lateral) and cuboid.

• Navicular is block-shaped that lies anterior to the talus.

TARSAL BONES

These are five miniature long bones, which together constitute the metatarsus. 

They are numbered from medial to lateral sides as 1st, 2nd, 3rd, 4th, and 5th metatarsals. 

Each of the five metatarsal bones consists of a proximal base, a shaft (body), and a distal head is rounded for articulation with the base of the proximal phalanx. 

Phalanges (Toe Bones)

The phalanges of the great toe are proximal and distal: and the phalanges of the other toes are proximal, middle and distal.

Each phalanx bears base, shaft and head.

JOINTS OF THE UPPER LIMB

Learning Outcome

1. Name the joints of upper limb with its types 

2. Describe shoulder joint with diagram

3. Mention the ligament of shoulder joint

4. How the elbow joint is formed 

5. Name the joints of the lower limb

6. Write short note on: knee joint

7. How the hip joint and knee joint are formed 

8. Describe intervertebral disc with functions

SHOULDER JOINT (Glenohumeral Joint)

Questions

➤ Describe the shoulder joint with diagram. 

➤ How the shoulder joint is formed? / Mention the ligaments of shoulder joint.

Definition :

The shoulder joint is a joint between the head of humerus and glenoid fossa of the scapula. 

Formation:

The shoulder joint is formed by the glenoid cavity of the scapula and the head of humerus.

Structure:

• The articular surfaces of the shoulder joint are the large spherical head of the humerus and the small glenoid cavity of the scapula. Each of the surfaces is covered by articular cartilage.

• The glenoid cavity is deepened and expanded peripherally by a rim of fibrocartilage, the glenoid labrum. It provides additional stability without limiting movement.

• The tendon of the long head of the biceps brachii muscle extends through the joint cavity and attaches to the upper rim of the glenoid cavity. 

Ligaments

• capsular ligament (joint capsule)

• glenohumeral (superior, middle, inferior) ligaments

• coracohumeral ligament

• transverse humeral ligament.

Factors providing stability to shoulder joint

1. Ligaments

2. Rotator cuff (musculotendinous cuff)

3. Coracoacromial arch

4. Long head of biceps tendon

5. Glenoid labrum

■  Rotator cuff or musculotendinous cuff is formed by the muscles (and their tendons) present in the shoulder. The muscles forming the rotator cuff are subscapularis, supraspinatus, infraspinatus and teres minor. 

Muscles and movements at shoulder joint

The shoulder joint allows movement in all directions: flexion, extention, abduction, adduction, medial rotation, lateral rotation, and circumduction.

Muscles producing movements at shoulder joint

MOVEMENT - MUSCLES

Flexion - Coracobrachialis, pectoralis major

Extension - Latissimus dorsi, teres major

Abduction - Deltoid, supraspinatus

Adduction - Latissimus dorsi, pectoralis major

Circumduction - Combination of actions of above muscles

ELBOW JOINT 

Type:

Hinge type of synovial joint

Question

➤ How the elbow joint is formed?

Formation of elbow joint

[NOTE: The elbow joint actually includes two articulations: 

(i) Humero-ulnar - Between the trochica of the humerus and trochlear notch of the ulna, and 

(ii) Humero-radial - Between the capitulum of the humerus and the head of radius.

Articular surfaces: Trochlea of humerus with the trochlear notch of ulna, and capitulum of humerus with head of radius.

Ligament: Capsular, radial collateral and ulnar collateral.

Movements: Flexion and extension.

• The main flexor at the elbow joint is biceps. 

• The extensor at the elbow joint is triceps.

RADIOULNAR JOINTS 

Formation

The radius and ulna form two joints between them as follows-

Muscles and movements

Movements taking place at the radioulnar joint are- Supination and pronation 

• Supination is caused by the supinator and biceps muscles 

WRIST JOINT (Radiocarpal Joint)

Definition

It is a joint between the lower end of radius and carpus.

Type: Ellipsoid type of synovial joint.

Articular surfaces

• The proximal articular surface is formed by the inferior surface of the lower end of the radius.

• The distal articular surface is formed by the proximal surfaces of the scaphoid, lunate and triquetral.

Ligaments

1. Capsular ligament (joint capsule)

2. Radial collateral ligament

3. Ulnar collateral ligament

4. Palmar radio-carpal ligament 

5. Palmar ulno-carpal ligament

6. Dorsal radio-carpal ligament

Muscles and movements

The following movements take place at the wrist joint:

Muscles producing movements at wrist joint

MOVEMENT - MUSCLES

Flexion - Flexor capri radialis, flexor carpi ulnaris

Abduction - Flexor carpi radialis, extensor carpi radialis (longus, brevis), abductor pollicis longus

JOINTS OF THE LOWER LIMB

Questions

Name the point of the limb.

Mention the joints of the lower limb.

HIP JOINT

Definition:

The hip joint is a ball and socket type of synovial joint between the head of the femur and the acetabulum of the hip bone.

Questions

➤ How hip joint is formed?

Formation of Hip Joint

The hip joint is formed by the spherical head of the femur and the cup-shaped acetabulum of the hip bone.

Articular surfaces:

• The head of the femur, and 

• Acetabulum of the hip bone

Structure:

• The articular surfaces are covered by the articular hyaline cartilage expect for a small pit the fovea capitis of the head of the femur (where the ligamentum teres is attached)

• The joint cavity is deepened by the acetabular labrum, a ring of fibrocartilage attached to the rim of the acetabulum.

Ligaments

1. Capsular ligament (Joint capsule)

2. Iliofemoral ligament

3. Pubofemoral ligament

4. Ischiofemoral ligament

5. Transverse acetabular ligament

6. Ligamentum teres (ligament of the head of the femur)

Muscles producing movements at hip joint

MOVEMENTS - MUSCLES

Flexion - Psoas, Iliacus, sartorius

Extension - Gluteus maximus, hamstring muscles

Abduction - Gluteus medius and minimus, sartorius

Adduction - Adductors (longus, brevis and magnus)

Medial rotation - Anterior fibres of gluteus minimum and medius, tensor fascia lata

Lateral rotation - Piriformis, obturator externus, obturator internus, gemelli and quadratus femoris

KNEE JOINT

Questions

► Write short note on: knee joint. / Describe the knee joint with diagram.

Definition

The knee joint is the largest and most complex joint of the body situated in the lower limb. 

Type: It is a modified hinge joint.

Question

► How the knee joint is formed?

Formation of Knee Joint

The knee joint is formed by the condyles of the femur, the condyles of the tibia and the posterior surface of the patella.

Articular surfaces:

(i) Medial and lateral condyles of the tibia

(ii) Posterior surface of the patella, articulating the patellar surface area between femoral condyles.

The articular surfaces are all enclosed within a single articular cavity.

Joint capsule:

• The fibrous capsule is very thin and surrounds the joint. It is deficient anteriorly, where it is replaced by the tendon of the quadriceps femoris, patella, and ligamentum patellae.

• Synovial membrane lines the inner aspect of the fibrous capsule and the portions of the bones enclosed within it. It covers the cruciate ligaments and the pads of fat.

Intracapsular structures :

(1) Two cruciate ligaments - anterior and posterior. These cross each other, extending from the intercondylar notch of the femur to the intercondylar eminence of the tibia. 

(2) Medial and lateral menisci (semilunar cartilage) - These are crescent-shaped intra- articular discs of white fibrocartilage. They lie on top of the articular condyles of the tibia. 

(3) Bursae and pads of fat.

External ligaments:

• Ligamentum patella

• Medial collateral ligament 

• Lateral collateral ligament

• Oblique popliteal ligament 

• Arcuate popliteal ligament 

• Transverse ligament

Muscles and movements

The following movements occur at knee joints- 

1. Flexion

2. Extension } Main / Active movement

3. Medial rotation)

4. Lateral rotation } Conjunct movements

Muscles producing movements at knee joint

Movements - CHIEF MUSCLES

Flexion - Semimembranosus, semitendinosus, biceps femoris

Extension - Quadriceps femoris

Medial rotation - Semitendinosus, semimembranosus, popliteus

Lateral rotation - Biceps femoris

ANKLE JOINT

Definition: The ankle joint is a strong weight-bearing joint of the lower limb.

Type: Hinge type of synovial joint.

Formation: The ankle joint is formed by the distal end of the tibia and its malleolus (medial malleolus), the distal end of the fibula (lateral malleolus) and the talus.

Articular surfaces:

1. The proximal articular surface of the ankle joint is formed by the articular facets of the - 

• lower end of tibia including its medial malleolus, and 

• lateral malleolus.

These together form a deep tibiofibular socket.

2. The distal articular surface of the ankle joint is formed by the articular facets on the upper, medial, and lateral aspects of the body of the talus.

Joint capsule:

• The fibrous capsule surrounds the joint completely.

• The synovial membrane lines the inner surface of the joint capsule, but ceases at the periphery of the articular cartilage.

Ligaments

1. Deltoid ligament 

2. Anterior ligament

3. Posterior ligament

4. Medial ligament 

5. Lateral ligament

JOINTS OF THE FOOT

There are a number of synovial joints that are formed in the foot between the tarsal bone between the tarsal and metatarsal bones, between the metatarsals and proximal phalanges are between the phalanges.

Thus the joints of the foot include:

■ Intertarsal - subtaler (talocalcaneal) [Plane type of synovial joint]  - Talocalcaneonavicular [Ball and socket type of synovial joint]

 - Calcaneocuboid [Saddle type of synovial joint) 

 - Transverse tarsal (midtarsal) [Compound joint]

■ Tarsometatarsal - Plane type of synovial joint.

■ Metatarsophalangeal - Ellipsoidal type of synovial joint

CHAPTER SUMMARY

Skeletal system 

• The skeletal system consists of the bones of the skeleton and their joints.

Divisions of skeletal system 

• The appendicular skeleton includes the bones of the upper and lower limbs and the bones of the pelvic girdle and the pectoral girdle.

Axial skeleton

Skull

• The skull consists of cranial and facial bones; all are joined by immovable joints except the mandible.

• The cranial bones form the cranium which encloses the cranial cavity, containing the brain. 

• The frontal bone forms the forehead and superior surface of each orbit.

• The temporal bones form the sides and base of the cranium and fuse with the parietal bones along the squmosal suture.

• The sphenoid bone acts like a bridge, uniting the cranial and facial bones.

•  The cribriform plate of ethmoid contains perforations for olfactory nerves. The perpendicular plate of ethmoid forms part of the bony nasal septum.

• The right and left maxillary bones (maxillae) articulate with all the other facial bones except the mandible. Each maxilla contains a large air sinus.

• The lacrimal bones are within the orbit on its medial surface.

• The nasal bones articulate with the frontal bone and maxillary bones.

• The inferior nasal conchae inside the nasal cavity aid the superior and middle nasal conchae of the ethmoid bone to slow incoming air. 

Vertebral column

• The vertebral column consists of 24 vertebrae, the sacrum and coccyx, and the column encloses the spinal cord.

• The vertebrae are grouped as cervical (7), thoracic (12), and lumbar (5) 

• The adjacent vertebrae of the vertebral column are articulated by the intervertebral discs, which act as shock absorbers and provide flexibility to the vertebral column. 

Vertebrae (Singular- vertebra) 

• General structure of vertebrae: With the exception of first and second cervical vertebrae (C1, C2), all vertebrae have a body, two transverse processes, two superior and two inferior articular processes.

• The first two cervical vertebrae are unique. The atlas rotates on the axis when the head is turned. 

• Cervical vertebrae are distinguished by the shape of the body and by foramen transversarium (transverse foramen).

• Thoracic vertebrae have distinctive heart-shaped bodies; have facets on the body and transverse processes for articulation with the ribs. 

• Lumbar vertebrae have heavy and strong bodies.

• A its base, the sacrum articulates with the body of 5th lumbar vertebra. 

• The coccyx is formed of three to five rudimentary vertebrae and forms the inferior end of the vertebral column.

• The skeleton of thorax consists of the thoracic vertebrae, the ribs, and the sternum. These bones together form the thoracic cage or rib cage.

• There are 12 pairs of ribs. Ribs 1 to 7 are true ribs. The inferior two pairs (ribs 11 and 12) of false ribs are floating rbs.

Appendicular skeleton

• Pectoral (shoulder) girdle: Each arm articulates with the trunk at the pectoral girdle, which consist of the scapula and clavicle.

• The scapula articulates with the clavicle and with the humerus. 

• The clavicle holds the scapula laterally away from the thorax. The sternoclavicular joint (between medial end of the clavicle and the sternum) is the only attachment points of the pectoral girdle to the axial skeleton.

• Besides the scapula and clavicle (bones of pectoral girdle) the bones of the upper limb include: humerus, ulna, radius, carpals, metacarpals, and phalanges. 

• The skeleton of the arm is composed solely of the humerus. The greater tubercle and lesser tubercle are prominent feature of the upper end of the humerus. They are important sites for muscle attachment. Other prominent landmarks of the humerus include the deltoid tuberosity, medial and lateral epicondyles, and the articular condyle.

• The skeleton of the forearm is composed of the radius and ulna.

• The radius is the lateral (thumb side) bone of the forearm, while the ulna is the medial bone. 

The olecranon fossa of humerus accommodates the olecranon process of ulna during extension of the arm. The coronoid fossa of humerus accommodates the coronoid process of ulna. 

• The hip joint is a ball and socket type of synovial joint, formed by the acetabulum of hip bone and the head of the humerus.

The hip joint permits flexion and extension, adduction and abduction, circumduction, and rotation.

• It is a complicated hinge joint formed by the articulation of the condyles of the tibia and femur (and anteriorly by the patella and patellar surface of the femur).

• The carpals are arranged into two rows. The distal carpal bones articulate with the metacarpal bones of the palm. The melacarpal bones articulate with the proximal phalanges. The thumb (or pollex) has two phalanges, but other fingers have three phalanges. 

• The pelvic girdle consists of two hip bones that are joined to the sacrum posteriorly and to each other anteriorly. 

• The hip bones secure the lower limbs to the axial skeleton.

• The lium forms the upper portion of a hip bone and joins with the sacrum to form a sacroiliac joint. 

• The ischium forms the inferior, posterior portion of a hip bone and supports the body when sitting.

• The pubis forms the lower, anterior part of a hip bone. The pubic bones unite anteriorly to form the symphysis pubis. 

• The pelvis consists of the hip bone, sacrum and coccyx.

• Each lower limb consists of a femur, a patella, a tibia, a fibula, tarsals, metatarsals, and phalagnes.

• Its ball-shaped head articulates with the acetabulum of the hip bone to form a hip joint.

• The patella is a sesamoid bone in the anterior portion of the knee joint.

• The tibia presents tibial tuberosity on the anterior surface just below the condyles. A ligament from the patella attaches at the tibial tuberosity. 

Other tibial landmarks are the anterior crest and the medial malleolus. 

The tibia articulates with the femur at the knee joint, and with the talus distally to form the ankle joint.

• The fibula lies lateral to the tibia. The fibular head articulates with the tibia below the knee, and the lateral stabilizes the ankle.

• Out of seven tarsal bones only the talus articulates with the tibia and fibula at the ankle joint. When we stand normally, most of our weight is transferred to the calcaneus, and the rest is passed on to the metatarsal bones.

JOINTS

• The joints of the upper limb include shoulder joint, elbow joint, wrist joint and other small joints of the hand.

• The shoulder joint is a ball-and-socket type of synovial joint formed by the glenoid cavity of the scapula and the head of the humerus. These bones are bound together by a ligamentous articular capsule that is lined by a synovial membrane. The articular capsule of shoulder joint is lax and poorly reinforced by ligaments. The tendons of the biceps brachii and rotator cuff muscles help to stabilize it. 

The shoulder joint is the most freely movable joint of the body; it allows all angular and rotational movements.

• The elbow joint is a hinge type of synovial joint in which the ulna (and radius) articulates with the humerus. It is extremely stable because of extensive ligaments and the shapes of the articulating elements.

• The joints of the lower limb include the hip, knee, ankle and other small joints of the foot. 

The patella is embedded within a tendon that supports the front of the joint.

The articular surfaces of the joint are shallow and condyloid. C-shaped menisci deepen the articular surfaces. 

surfaces. The joint cavity is enclosed by a capsule only on the sides and posterior aspects, Several ligaments give stability to the joint.

Extension, flexion and some rotation are allowed.