HUMAN BODY CAVITIES - Thoracic Cavity | Abdominal Cavity | Pelvic Cavity

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Principal Body Cavities 

Cranial Cavity

Thoracic Cavity

• Pleural cavity

• Pericardial cavity and pericardium

• Mediastinum

Abdominopelvic Cavity

• Abdominal cavity

• Pelvic cavity

Abdominal Regions

Other cavities of the body

Learning Outcome

1. What are the principal contents of thoracic cavity

2. What is pericardium? / Define pericardium.

3. Give the contents of pericardium.

4. Define mediastinum. / What is mediastinum

5. Write down the contents of mediastinum.

6. Give the boundary and contents of the superior mediastinum. 

7. Give the contents of middle mediastinum

8. Give the contents of abdominal cavity 

9. How abdomen is divided into regions

10. Write about division of the abdomen into nine regions 

11. Write short note on Regions of abdomen

12. Draw and label the different anatomical regions of the abdomen 

13. Name the different regions of abdomen. Draw a diagram and label it

14. Name the nine regions of abdomen with diagram.

15. Mention the contents of hypogastric region. / List the contents of hypogastrium

16. Name the regions where the following organs are placed: liver, stomach, kidney,     appendix, caecum, and urinary bladder. 

17. What are visceral organs

PRINCIPAL BODY CAVITIES

Definition of body cavities

Body cavities are spaces within the body that protect, separate, and support internal organs.

Principal body cavities

There are two principal cavities of the body - the dorsal (posterior) and ventral (anterior) cavities which are again divided into small cavities as follows:

1. Dorsal body cavities

2.Ventral body cavities

CRANIAL CAVITY

The cavity within the skull that is formed by the cranial bones, is called cranial cavity.

Boundary:

• Anteriorly - frontal bone (1) 

• Laterally - temporal bones (2)

• Posteriorly-occipital bone (1) 

• Superiorly-parietal bones (2)

• Inferiorly - sphenoid (1) and ethmoid bone (1) and parts of the frontal, temporal and occipital bones.

Content of cranial cavity: Brain.

THORACIC CAVITY

The cavity situated in the upper part of the trunk of the body (i.e. thorax) is called thoracic cavity or chest cavity. It is in between the neck above and the abdomen below.

Boundary:

The boundaries of the thoracic cavity are formed by bony framework of thorax (thoracic cage) and supporting muscles as follows:

• Anteriorly - the sternum and and costal cartilages of the ribs 

• Posteriorly - the thoracic vertebrae (12) 

• Superiorly - the structures forming the root of the neck 

Subdivisions:

Within the thoracic cavity are the pericardial cavity (a fluid-filled space that surrounds the heart) and two pleural cavities (each surrounds the lung).

What are the principal contents of thoracic cavity?

Contents of thoracic cavity

 • the heart, aorta, superior vena cava and inferior vena cava, numerous other blood vessels.

 • the oesophagus

 • lymph vessels and lymph nodes 

 • nerves.

What is pleural cavity?

Pleural Cavity

 • Each lateral compartment of thoracic cavity is occupied by a lung enclosed in the serous sac called pleural cavity.

 • In other words: The space between the visceral pleura and parietal pleura is called pleural cavity. This is a potential space.

Pericardial Cavity and Pericardium

What is pericardium? /Define pericardium. 

Give the contents of pericardium.

Pericardium

The pericardium is a fibroserous sac which encloses the heart and the roots of great vessels.

Layers of pericardium

The pericardium has two layers:

• Fibrous pericardium.

• Serous pericardium-(composed of two layers: parietal pericardium and visceral pericardium).

Contents of pericardium

1. Heart with cardiac vessels and nerves

2. Ascending aorta

3. Pulmonary trunk

5. Terminal part of the inferior vena cava 

6. Terminal parts of the pulmonary veins.

Functions (importance) of pericardium

• Restricts excessive movements of the heart. 

• Serves as a lubricated container in which the heart can contract and relax smoothly.

• Limits the cardiac distension.

What is pericardial cavity? Give its content.

Pericardial Cavity

The pericardial cavity is a potential space between the parietal pericardium and the visceral pericardium. This surrounds the heart.

Content: A thin film of serous fluid, known as pericardial fluid.

This fluid lubricates the apposed surfaces of the heart and allows it to beat smoothly.

Mediastinum

Define mediastinum/What is mediastinum?

The mediastinum is the middle space in the thoracic cavity in between the lungs.

Boundaries of mediastinum

• Anteriorly: Sternum

• Posteriorly: Vertebral column

• Superiorly: Thoracic inlet 

• Inferiorly: The diaphragm

• On each side: mediastinal pleura

Write down the contents of mediastinum.

Contents of mediastinum

1. Heart enclosed in the pericardial sac

2. Major arteries and veins such as thoracic aorta, pulmonary trunk etc.

3. Trachea

4. Oesophagus

5. Thoracic duct

6. Thymus

7. Sympathetic trunk, vagus nerves, phrenic nerve, etc. 

8. Lymph nodes

Classification/Subdivisions of Mediastinum

1. Superior mediastinum

2. Inferior mediastinum

• Anterior mediastinum
•  Middle mediastinum
•  Posterior mediastinum

Superior mediastinum

 • Superior mediastinum is the area above an imaginary plane extending from the sternal    angle (the junction between the manubrium and the body of the sternum) to the    intervertebral disc between fourth and fifth thoracic vertebrae.

 • The area below the above imaginary plane is the inferior mediastinum.

Give the boundary and contents of the superior mediastinum.

Boundary of superior mediastinum:

• Anteriorly- Manubrium Sterni

• Posteriorly- Upper four thoracic vertebrae 

• Superiorly-Plane of the thoracic inlet

• On each side - Mediastinal pleura

Contents of superior mediastinum:

1. Trachea and oesophagus

2. Muscles: Origins of - stemnohyoid, sternothyroid and longus coli muscles 

3. Arteries: Arch of the aorta, brachiocephalic artery, left common carotid artery, and left subclavian artery

4. Veins: Right and left brachiocephalic veins, superior vena cava, and left superior intercostal vein

5. Nerves: Vagus, phrenic, cardiac and left recurrent laryngeal nerves

6. Thymus

7. Thoracic duct

8. Lymph nodes

Anterior mediastinum

Boundaries of anterior mediastinum:

• Anteriorly- Body of sternum

• Posteriorly- Pericardium

• Superiorly-An imaginary plane separating the superior mediastinum from the inferior   mediastinum 

• On each side - Mediastinal pleura

Contents of anterior mediastinum:

1. Sternopericardial ligaments

2. Lymph nodes with lymphatics

3. Small mediastinal branches of internal thoracic artery

4. Thymus (lowest part) 

5. Areolar tissue.

Middle mediastinum

Boundaries of middle mediastinum:

• Anteriorly - Sternopericardial ligaments

• Posteriorly-Oesophagus, descending thoracic aorta and azygos vein.

• On each side - Mediastinal pleura.

Give the contents of middle mediastinum

Contents of middle mediastinum:

1. Heart enclosed in pericardium 

2. Bifurcation of trachea, right and left principal bronchi

3. Arteries: Ascending aorta, pulmonary trunk, and two pulmonary arteries.

4. Veins: Superior vena cava, azygos vein, right and left pulmonary veins. 

5. Nerves: phrenic nerve and deep cardiac plexus

6. Tracheobronchial lymph nodes.

Posterior Mediastinum

Boundaries of posterior mediastinum:

• Anteriorly - Pericardium, bifurcation of trachea, pulmonary vessels.

• Posteriorly-Lower eight thoracic vertebrae.

• On each side-Mediastinal pleura.

Contents of posterior mediastinum:

1. Oesophagus

2. Descending thoracic aorta and its branches

3. Veins: Azygos vein, hemiazygos vein, and accessory hemiazygos vein.

4. Nerves: Vagus nerve, splanchnic nerves

5. Lymph nodes and lymphatics.

6. Thoracic duct

ABDOMINAL CAVITY

Definition

•  Abdominopelvic cavity: The abdomen contains a cavity known as abdominopelvic cavity, which is subdivided by    the plane of the pelvic inlet into an upper part, the abdominal cavity.

Boundaries of abdominal cavity

• Superiorly- The diaphragm (it separates the abdominal cavity from the thoracic cavity).

• Anteriorly-The muscles forming the anterior abdominal wall. 

• Posteriorly-The lumbar vertebrae and muscles forming the posterior abdominal wall.

• Inferiorly - It is continuous with the pelvic cavity.

Give the contents of abdominal cavity.

Contents of abdomen / abdominal cavity

•  Digestive tract: Abdominal part of oesophagus, stomach, small intestine, with caecum   and appendix.

•  Organs associated with digestive tract: Liver, gallbladder and pancreas.

•  Urinary system: Kidneys, ureters (upper part)

•  Other organs: Adrenal (or suprarenal) gland, spleen.

• Large and small blood vessels (eg. abdominal aorta and its branches, inferior vena cava  and its tributaries etc.), lymphatics and nerves

•  Lymph nodes.

PELVIC CAVITY

Its lower boundary is the pelvic floor. Pelvic cavity is considered as part of the abdomen / abdominal cavity

Boundaries of pelvic cavity:

•  Superiorly - continuation of the abdominal cavity.

•  Anteriorly - Pubic bones 

•  Posteriorly -Sacrum and coccyx

•  Laterally - Hip bones

•  Inferiorly - The muscles of the pelvic floor

Contents of pelvic cavity:

•  Lower part of digestive tract : Sigmoid colon, rectum, and anal canal

•  Urinary bladder, lower parts of ureters and urethra

•  Reproductive organs: Ovaries, uterus, uterine tubes and vagina (in female). 

  Prostate gland, seminal vesicles, spermatic cords, ductus deferens (vas deferens),   ejaculatory ducts (in male)

•  Many blood vessels, nerves, lymphatics, and muscles.

ABDOMINAL REGIONS

The abdomen (or abdominal cavity) can be divided into nine regions by two vertical lines and two horizontal planes through anterior abdominal wall.

 •  The right and left vertical lines: right mid-clavicular line and left mid-clavicular line. These lines pass through the mid-inguinal points; i.e. a point on each inguinal ligame midway between the anterior superior iliac spine and the pubic symphysis. 

 •  Two horizontal planes are:

   (1) Transpyloric plane, it lies horizontally midway between the jugular notch of the sternum and the pubic symphysis, i.e. approximately midway between the xiphoprocess and the umbilicus, at the level of the lower part of the body of the first lumbar vertebra

  (ii) Trnastubercular plane, it passes horizontally through the tubercles of the iliac crests the level of the fifth lumbar vertebra.

Regions of Abdomen

1. Right hypochondriac (right hypochondrium)

2. Left hypochondriac (left hypochondrium)

3. Epigastric (epigastrium) 

4. Right lumbar region

5. Left lumbar region

6. Umbilical region

7. Right iliac

8. Left iliac

9. Hypogastric (or hypogastrium) or pubic

Contents of Abdomen regionally

Right hypochondrium:

• Liver (right lobe) 

• Gallbladder

• Upper part of right kidney

Epigastrium:

• Stomach (pylorus)

• Part of liver

• Pancreas

• Duodenum

• Suprarenal gland

• Abdominal aorta

Right lumbar region:

• Right kidney

• Right ureter

• Ascending colon

• Part of duodenum

• Part of coils of jejunum

Right iliac region (fossa):

• Caecum

• Vermiform appendix

• Part of right ureter

• Right ovary and part of uterine tube (in female) 

• Right vas deferens (in male)

Left hypochondrium:

• Spleen

• Transverse colon

• Some parts of stomach 

• Tail of pancreas

• Upper part of left kidney

Left lumbar region:

• Left kidney

• Left ureter

• Descending colon

• Some parts of jejunum and ileum

Umbilical region:

• Part of stomach

• Head of pancreas

• Duodenum

• Transverse colon 

• Parts of jejunum and ileum

• Urinary bladder (when filled with urine)

Left iliac region (fossa):

• Sigmoid colon

• Part of left ureter

• Left ovary (in female)

• Left vas deferens (in male)

Mention the contents of hypogastric region. / List the contents of hypogastrium.

Contents of hypogastrium :

In both sexes-

  • Urinary bladder

  • Lower part of ureters

  • Rectum

  • Coils of small intestine

  • Sigmoid colon

In male-

  • Prostate

  • Vas deferens

  • Seminal vesicle

In female-

  • Uterus 

  • Uterine tube

  • Round ligament

Name the regions where the following organs are placed: liver, stomach, kidney, appendix, caecum, and urinary bladder.

(i)  Liver -     Right hypochondriac (whole region), epigastrium (greater part) and left

                hypochondrium (very small part) 

(ii)  Stomach -  Epigastric, umbilical and left hypochondriac regions

(iii)  Kidney -  Epigastric, right and left hypochondriac, right and left lumbar regions

(iv)  Appendix - Right iliac fossa (region) 

(v)  Caecum -    Right iliac fossa (region)

(vi)  Urinary bladder- 

                • When empty, it lies entirely in the hypogastrium

                • When filling, it expands and extends up to the umbilical region or even epigastric region of the abdominal cavity

Quadrants of abdomen

The abdomen can also be divided simply into four quadrants (one-fourth) by a vertical line and a horizontal line passing through the umbilicus. The names of the abdominal quadrants are:

 • Right upper quadrant 

 • Left upper quadrant

 • Right lower quadrant

 • Left lower quadrant

Other cavities of the body

The body also contains:

 • An oral cavity (the mouth).

 • A nasal cavity (located in the nose).

 • Middle ear cavity (which contains the small bones of the middle ear). 

 • Synovial cavities (enclosed within the capsules surrounding freely moveable joints).

Serous cavities: pleural, pericardial, and peritoneal

Internal organs that require freedom to move are partially enclosed by a potential space to facilitate this movement. This space develops into the serous cavities (serous because they contain a small amount of lubricating fluid) and the membrane that lines such cavity is a serous membrane.

 • Pleural cavities permit movement of the lungs during breathing; 

   serous membrane: pleura.

 • Pericardial cavity permits movement of the heart as it beats; 

   serous membrane: pericardium. 

 • Peritoneal cavity permits movement of intestines during digestion;

   serous membrane : peritoneum.

What are visceral organs?

Visceral organs

Visceral organs, or viscera, are those that are located within the anterior body   cavities.

 • Viscera of the thoracic cavity are the heart and lungs.

 • Viscera of the pelvic cavity are the urinary bladder, portion of the large intestine, and internal organs of the reproductive system.

CHAPTER SUMMARY

• The meninges are the protective tissues that line the cranial and vertebral 

• The diaphragm divides the ventral part of the body into (superior) thoracic and (inferior) abdominopelvic cavities.

• The thoracic cavity consists of two pleural cavities (each surrounding a lung) separated by a tissue mass known as the mediastinum. Within the mediastinum is the pericardial cavity, which surrounds the heart. 

• The abdominopelvic cavity consists of the cavity and the pelvic cavity and

  umbilical, left lumbar, right inguinal (lilac), hypogastric (pubic), and left inguinal (iliac).