Human Muscular System - Skeletal Muscles | Muscles Facial Expression

Muscular System

CHAPTER PREVIEW

Introduction

■ Definitions and functions

■ Names of skeletal muscles 

■ Ways of muscular attachment

Major Skeletal Muscles

■ Head and Neck muscles:

• Muscles of Facial Expression and Mastication

• Muscles of the Neck 

• Muscles of the tongue

■ Muscles of the thorax: 

• Respiratory muscles

• Intercostal muscles

■ Muscles of the trunk : 

• Muscles of the back

• Muscles of the abdominal wall

■ Muscles of the pelvic floor

■ Muscles acting on the pectoral girdle

■ Muscles of the upper limb

■ Muscles of the hip

■ Muscles of the lower limb

Learning Outcome

1. What are the muscles of the arm & forearm? Give their nerve supply. 

2. Name the muscles of the anterior abdominal wall.

3. Enumerate the pelvic muscles. 

4. Name the muscles of respiration.

5. Name the muscles of tongue. 

6. Write down the origin, insertion, blood supply and nerve supply of -

  • Deltoid

  • Biceps brachii 

  • Gluteus maximus

INTRODUCTION

Definitions and Components of Muscular System

■ The muscular system is the series of muscles throughout the body that move the skeleton, maintains posture and generate heat through cell metabolism. 

■ The musculoskeletal system is made up of - bones and joints of the skeleton, muscles,

cartilage, tendons, ligaments and other connective tissues. 

■ Tendon: A tendon is a band or cord of collagen fibres that provides attachment to the bone.

■ Aponeurosis: An aponeurosis is a broad flat sheet of densely arranged collagen fibres that attaches a muscle to the bone or another muscle.

Functions of Muscular System 

1. Produces skeletal movement.

2. Maintains posture and body position. 

3. Supports soft tissue

4. Guards entrances and exits through mouth, anus and urethral opening.

5. Maintains body temperature.

Functions of Musculoskeletal System 

• The musculoskeletal system gives protection and support to the internal structures and organs of the body

• It allows movement

• Gives shape to the body 

• Produces blood cells

• Stores calcium and phosphorus 

• Produces heat

• Blood circulation: Cardiac muscle aids pumping action of the heart by aiding blood circulation. 

Names of Skeletal Muscles (Muscle Terminology)

A few of the criteria used in naming muscles and examples of terms found in the names of muscles are given below: 

• Terms indicating action: extensor, flexor, abductor, adductor etc.

• Shape: trapezius (trapezium-shaped), deltoid (triangular), piriformis (pear-shaped). 

• Number of origin: biceps (two heads), triceps (three heads), quadriceps (four heads). . • Relative position: external, internal, abdominal etc.

• Location: intercostal (between ribs), pectoralis (chest), tibialis (close to tibia)

• Bones to which muscle is attached : sternohyoid (sternum and hyoid), carpi radialis muscles (carpal bones and radius)

• Orientation of fibres: oblique (diagonal), rectus (straight), transverse (across). 

Terms of Muscular Attachment

■ Origin: It is the beginning of the muscle which remains stationary.

■ Insertion: It is the other end which moves during contraction.

Ways of muscular attachment: 

Muscles may be attached to bone three different ways - 

1. Directly to the periosteum,

2. By means of a tendon, and 

3. With an aponeurosis.

Muscle grouping

Muscles can be grouped by their primary actions into : 

1. For example - the biceps brachii muscle is a prime move that flexes the elbow.

2. Antagonists are prime movers whose actions oppose that of the agonist under consideration. 

3. Synergists are the muscles that assist the agonists to reduce undesired action or unnecessary movement.

Broad Groups of Muscles 

1. Muscles of the axial skeleton include those used in facial expression, mastication, neck movement, and respiration; those that act on the abdominal wall; those that move the vertebral column. 

2. Muscles of the appendicular skeleton 

The muscles of the appendicular skeleton include those of the pectoral girdle, arm, forearm, hand, thigh, leg and foot.

MAJOR SKELETAL MUSCLES

MUSCLES OF THE NECK AND FACE

Muscles of neck muscles

There are several pairs of muscles in the neck that can be grouped according to their location. The sternocleidomastoid and trapezius are the two largest muscles in the neck. Neck muscles are located at the front, back, and sides of the neck.

Simply, neck muscles are:

1. Platysma

2. Stemocleidomastoid

3. trapezius 

4. Scalenes

5. Suprahyoid muscles: Digastries, Stylohyoid, Mylohyoid, Geniohyoid 

6. Infrahyoid muscles: Sternohyoid, Stemothyroid, Thyrohyoid, Omohyoid

However, the neck region is home to more than just neck muscles; muscles of the head spine, and thorax also attach in this area.

Functions of neck muscles

Neck muscles are responsible for - 

• Head movement: flexing, extending and turning the head

• Assisting in swallowing

• Helping to elevate the rib cage during inspiration.

FACIAL MUSCLES (Muscles Facial Expression)

The facial muscles are subcutaneous muscles. Since these muscles are inserted into skin these bring out various facial expressions such as anger, sadness, happiness, fear, disgust, pain, surprise etc. So, these are secondarily known as muscles of facial expression.

The orbital facial muscles: 

1. Occipitofrontalis (frontalis contributes to this functional group)

2. Levator palpebrae superioris 

3. Orbicularis oculi

4. Corrugator supercilii

Nasal facial muscles:

5. Procerus

6. Compressor naris

7. Dilator naris

8. Depressor septi

Oral facial muscles (Muscles around the lips):

9. Orbicularis oris

10. Buccinator

11. Levator labii superioris alaeque nasi

12. Zygomaticus major and minor

13. Levator labii superioris

14. Levator anguli oris 

15. Depressor anguli oris

16. Depressor labii inferioris

17. Mentalis

18. Risorius

Neck muscle:

19. Platysma

MUSCLES OF MASTICATION

• Temporalis 

• Medial pterygoid

• Masseter 

• Lateral pterygoid

The temporalis and masseter are two major pairs of muscles raising the mandible in the process of mastication and speech

• Mylohyoid 

• Geniohyoid

Question 

► Name the muscles of tongue

Muscles of the tongue

■ Intrinsic muscles:

1. Superior longitudinal

2. Inferior longitudinal 

3. Transverse

4. Vertical

■ Extrinsic muscles:

1. Genioglossus

2. Hyoglossus

3. Styloglossus 

4. Palatoglossus

MUSCLES OF THE THORAX / RESPIRATORY MUSCLES

Muscles of the thoracic wall

Eleven pairs of intercostal muscles are in each of the intercostal spaces on the back and only 9 in front of chest, arranged from superficial to deep as follows: 

1. External intercostal muscles 

2. Internal intercostal muscles

3. Transversus thoracis muscles which are divisible into three parts, namely subcostalis, innermost intercostal (intercostalis intimi) and sternocostalis.

Intercostal space

The gaps between the ribs are called intercostals spaces. There are 9 intercostal spaces anteriorly and 11 intercostal spaces posteriorly. 

Contents of intercostals spaces:

• Intercostal muscles 

• Intercostal nerves

• Intercostal vessels and lymphatics

Intercostal nerve and vessels lie in between the internal and the innermost intercostals. In the intercostal space, the intercostal artery is accompanied by the intercostal vein and nerve, the relationship from above downwards being vein - artery - nerve (VAN).

Intercostal Muscles

• External intercostal muscles extend downwards and forwards from the lower border of the rib above to the upper border of the rib below.

• Internal intercostal muscles extend downwards and backwards from the lower border of the rib above to the upper border of the rib below, crossing the external intercostal muscle fibres at right angles.

• Intercostalis intimi is confined to the middle two-fourths of all the intercostal spaces.

Question

► Write down the muscles of respiratory system.

Muscles of Respiration

Respiratory muscles are of two types:

1. Inspiratory muscles 

2. Expiratory muscles

Inspiratory Muscles 

■ Primary (major) inspiratory muscles:

(i) The diaphragm 

(ii) External intercostal muscles

■ Accessory inspiratory muscles in forceful inspiration :

(i) Sternocleidomastoid

(ii) Scalene

(iii) Serratus anterior and pectoral muscles

(iv) Quadratus lumporum

Expiratory Muscles

■ Primarily no muscles are involved in quiet expiration. It is mostly passive and takes place by elastic recoil of lungs and thoracic cage.

■ Accessory expiratory muscles in forceful expiration:

(i) Internal intercostal muscles 

(ii) Muscles of the anterior abdominal wall

MUSCLES OF THE TRUNK

The muscles of the trunk stabilize the association between the appendicular and axial skeletons at the pectoral girdle, and stabilize and allow movement of the shoulders and upper arms.

■ Muscles of the back

There are 6 pairs of large muscles in the back, in addition to those forming the posterior abdominal wall. The arrangement of these muscles is the same on each side of the vertebral column.

The muscles of the back are 

(i)   Trapezius

(ii)  Latissimus dorsi 

(iii) Teres major

(iv)  Psoas

(v)   Quadratus lumborum 

(vi)  Erector spinae (sacrospinalis)

Note: The iliocostalis, longissimus, and spinalis groups of muscles are collectively called the erector spinae.

Question

Name the muscles of the anterior abdominal wall.

■ Muscles of the abdominal wall 

The abdominal wall consists of five pairs of muscles. From the surface inwards these are: 1. Rectus abdominis

2. External oblique 

3. Internal oblique

4. Transversus abdominis 

5. Quadratus lumborum

Functions: "Formation of the strong muscular anterior wall of the abdominal cavity" - This is the main function of the abdominal muscles.

When the muscles contract together they - 

• Compress the abdominal organs.

• Contraction of the muscles on one side only bends the trunk towards that side.

■ Linea alba: It is a very strong midline tendinous cord which divides the anterior abdominal wall longitudinally, extending from the xiphoid process of the sternum to the symphysis pubis.

MUSCLES OF PELVIC FLOOR

The pelvic floor is divided into two identical halves that unite along the midline. Each half consists of fascia and muscle. The muscles are:

• Levator ani 

• Coccygeus

Functions of pelvic floor :

• Supports the organs of the pelvis

MUSCLES ACTING ON PELVIC GIRDLE

1. Serratus anterior

2. Pectoralis minor 

3. Subclavius

4. Trapezius

5. Levator scapulae

6. Rhomboideus major

7. Rhomboideus minor

MUSCLES OF THE UPPER LIMB

Question

► What are the muscles of the arm & forearm? Give their nerve supply.

MUSCLES OF THE ARM

1. • Coracobrachialis

    • Biceps brachii

    • Brachialis

2. Muscle of the posterior compartment - Triceps brachii muscle. [This muscle is supplied by the radial nerve]

MUSCLES OF THE FOREARM

Muscles of front of the forearm (Flexor compartment of forearm) 

These muscles are organized into three layers. They are mostly innervated by the median nerve (except for the flexor carpi ulnaris and medial half of the flexor digitorum profundus, which are innervated by the ulnar nerve).

1. Superficial muscles:- Nerve supply

(i) Pronator teres - Median nerve

(ii) Flexor carpi radialis - Median nerve

(iii) Palmaris longus - Median nerve

(iv) Flexor carpi ulnaris - Ulnar nerve

2. Intermediate muscle:- Flexor digitorum superficialis - Median nerve

3. Deep muscles:-

(i) Flexor digitorum profundus - Medial half by ulnar nerve; lateral half by median nerve 

(ii) Flexor pollicis longus - Median nerve (anterior interosseous nerve)

(iii) Pronator quadrates - Median nerve (anterior interosseous nerve)

These muscles are organized into three layers.

1. Superficial muscles :-

(i) Anconeus 

(ii) Brachioradialis

(iii) Extensor carpi radialis longus

(iv) Extensor carpi radialis brevis

(v) Extensor carpi ulnaris

2. Intermediate muscles :-

(i) Extensor digitorum

(ii) Extensor digiti minimi

3. Deep muscles :-

(i) Supinator

(ii) Abductor pollicis longus

(iii) Extensor pollicis brevis

(iv) Extensor pollicis longus 

(v) Extensor indicis

Question

► Write down the ongin, insertion, blood supply and nerve of - Deltoid Biceps brichii.

DELTOID

Origin: 

• Spine of the scapula

• Acromion process of scapula

• Clavicle (lateral one-third) 

Insertion: Deltoid tuberosity of the humerus.

Blood Supply: Posterior circumflex humeral artery, (branch of axillary artery). 

Nerve supply: Axillary nerve. (C5. C6)

Actions:

(1) Abduction of shoulder joint. 

(2)Flexion, adduction and medial rotation of shoulder joint. 

(3) Extension, adduction and lateral rotation of the arm.

BICEPS BRACHII

Origin:

• Long head-Supraglenoid tubercle of the scapula

Insertion: Tuberosity of radius. 

Blood supply: Axillary artery.

Nerve supply: Musculocutaneous nerve.

Actions:

(1) Supination of the forearm.

(2) Flextion of the elbow joint, best in supinated position.

MUSCLES OF THE HIP

1. Anterior and posterior muscles that move the thigh at the hip joint:

• Iliacus

• Psoas major

• Gluteus maximus 

• Gluteus medius 

• Gluteus minimus 

• Tensor fasciae latae

2. Medial muscles that move the thigh at the hip joint: 

• Gracilis

• Pectineus

• Adductor longus

• Adductor brevis

• Adductor magnus

Question

▸ Write down the origin, insertion, blood supply and nerve supply of - Gluteus maximus.

GLUTUES MAXIMUS

It is the largest muscle in the gluteal region.

Origin:

• Iliac crest

• Sacrum

• Coccyx

•  Sacrotuberous ligament

• Fascia covering gluteus medius

Insertion:

• Iliotibial tract of fascia lata. 

• Gluteal tuberosity of proximal femur.

Blood supply: Superior and inferior gluteal artery.

Nerve supply: Inferior gluteal nerve. 

Action (Function):

• Powerful extensor of flexed femur at the hip joint.

Muscles of the lower limb

■ Muscles of the thigh that act on the leg:

• Sartorius

• Quadriceps femoris

• Rectus frmoris

• Vastus lateralis

• Vastus medialis

• Vastus intermedius

■ Hamstrings-

• Biceps femoris

• Semitendinosus

• Semimembranosus

■ Muscles of the leg that move the ankle, foot, and toes:

• Tibialis anterior

• Extensor digitorum longus

• Extensor hallucis longus

• Peroneus tertius.

• Peroneus longus.

• Peroneus brevis.

• Gastrocnememius.

• Soleus.

• Plantaries.

• Popliteus.

• Flexor hallucis longus

• Flexor digitorum longus

• Tibialis posterior

CHAPTER SUMMARY

INTRODUCTION

• The muscular system is the series of muscles throughout the body that move the skeleton, maintains posture and generate heat through cell metabolism. 

SKELETAL MUSCLES

• Skeletal muscles have names according to many criteria such as shape, position, number of origin, location etc. 

• Muscles are attached to bones by either tendons or aponeuroses. 

• Actions of skeletal muscles: A prime mover (agonist) produces the desired action, an antagonist produces an opposite action.

Major skeletal muscles 

• Muscles of facial expression originate on skull bones and insert on connective tissue of the skin.

• Muscles of mastication originate on fixed skull bones and insert on the mandible.

• Muscles that move the head occur in the neck and upper back.

• Muscles of the abdominopelvic wall connect the pelvic girdle, rib cage, and vertebral column. They include the rectus abdominis, external oblique, internal oblique, and transversus abdominis.

• Muscles that move the ribs occur between the ribs. They are the external intercostals and internal Intercostals. 

• They include the trapezius, rhomboideus major, levator scapulae, pectoralis minor, and serratus anterior.

• They include the biceps brachii, brachialis, brachioradialis, and triceps brachii. 

• Muscles that move the wrist and fingers are the muscles of the forearm. They include the flexor carpi radialis, flexor carpi ulnaris, palmaris longus, extensor carpi radialis longus, extensor carpi ulnaris, and extensor digitorum.

• They include the quandriceps femoris, biceps femoris, semitendinosus, semimembranosus, gracilis, and sartorius. 

• Muscles that move the foot and toes are the muscles of the lower leg. They include the gastrocnemius, soleus, peroneus longus, tibialis anterior, and extensor digitourm longus.