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Renin Angiotensin Mechanism.

Body Cavities

 Introduction to the Human Body: Body Cavities

Introduction:

  • Human beings are the most complex of all the living organisms.

  • Human body contains many organs which work in an organized manner for an efficient working of the human body.

  • The study of human body is divided broadly in two divisions,

    • Anatomy

    • Physiology.

  • Human Anatomy is the branch of science that deals with the study of structures of different body parts.

  • Human Physiology is the branch of science that deals with the study of functions of different body parts.

Human Anatomy: Study of Structure.

Human Physiology: Study Of Functions.

Body Cavities:

  • These are spaces in the body that protect, separate and support the internal organs of the body.

  • The body cavities are mainly divided into two types,

    • Dorsal Body Cavities.

    • Ventral Body Cavities.

  1. Dorsal Body Cavities:

  • They are present on the dorsal side of the body.

  • They are comparatively smaller as compared to the ventral body cavities.

  • They are classified as,

    • Cranial Cavity.

    • Vertebral Cavity.

  • Cranial Cavity:

    • It contains Brain.

    • Boundaries are formed by the bones of the skull (Fig. 1.1):

      • Anteriorly —1 frontal bone

      • Laterally — 2 temporal bones

      • Posteriorly — I occipital bone

      • Superiorly — 2 parietal bones

      • Inferiorly — I sphenoid and 1 ethmoid bone and parts of the frontal, temporal and occipital bones.

Fig. 1.1

  • Vertebral Cavity:

    • It contains “Spinal Cord.”

    • Boundaries:

      • Are made by bones of the vertebral column i.e. by vertebrae  and the intervertebral discs between the bodies of the vertebrae.

  1. Ventral Body Cavities:

  • They are present on the ventral side of the body.

  • They are much larger in size as compared to the dorsal body cavities.

  • They are further classified as followings,

    • Thoracic Cavity

    • Abdominal Cavity.

    • Pelvic Cavity.

  • Thoracic Cavity: 

    • It is formed by,

      • Anteriorly — the sternum and costal cartilages of the ribs

      • Laterally — 12 pairs of ribs and the intercostal muscles

      • Posteriorly — the thoracic vertebrae and the intervertebral discs between the bodies of the vertebrae.

      • Superiorly — the structures forming the root of the neck

      • Inferiorly — the diaphragm, a dome-shaped muscle.

    • Contents

      • The main organs and structures contained in the thoracic cavities are (Fig. 1.2):

        • the trachea, 

        • 2 bronchi, 

        • 2 lungs

        • the heart, 

        • aorta, 

        • superior and inferior vena cava,

        • numerous other blood vessels

        • the oesophagus

Fig. 1.2

  • The thoracic cavity is divided into three parts,

    • Pleural Cavity: One around each lungs, Contains fluid.

    • Pericardial Cavity: Around heart, Contains fluid.

    • Mediastinum: Central part extends from sternum to vertebral column and from first rib to diaphragm, contains all organs of thoracic cavity except lungs.

  • Abdominal Cavity:

    • This is the largest cavity in the body and is oval in shape (Fig 1.3).

    •  It is situated in the main part of the trunk and its boundaries are:

      • Superiorly — the diaphragm, which separates it from the thoracic cavity 

      • Anteriorly — the muscles forming the anterior abdominal wall 

      • Posteriorly —the lumbar vertebrae and muscles forming the posterior abdominal wall 

      • Laterally — the lower ribs and parts of the muscles of the abdominal wall 

      • Inferiorly — the pelvic cavity with which it is continuous.

Fig 1.3

The abdominal cavity is divided into the nine regions shown in Figure 1.4. 

Figure 1.4

  • Contents

    • the stomach, 

    • small intestine and most of the large intestine

    • the liver, gallbladder, bile ducts and pancreas.

    • the spleen

    • 2 kidneys and the upper part of the ureters

    • 2 adrenal (suprarenal) glands

    • numerous blood vessels

    • lymph vessels,

    • nerves

    • lymph nodes.

  • Pelvic Cavity:

    • The pelvic cavity is roughly funnel shaped and extends from the lower end of the abdominal cavity (Fig 1.4). 

    • The boundaries are:

      • Superiorly — it is continuous with the abdominal cavity 

      • Anteriorly — the pubic bones 

      • Posteriorly — the sacrum and coccyx 

      • Laterally — the innominate bones 

      • Inferiorly — the muscles of the pelvic floor.

Fig 1.4

  • The pelvic cavity contains the following structures: 

    • sigmoid colon, rectum and anus 

    • some loops of the small intestine 

    • urinary bladder, lower parts of the ureters and the urethra

    •  in the female, the organs of the reproductive system: the uterus, uterine tubes, ovaries and vagina.

    • in the male, some of the organs of the reproductive system: the prostate gland, seminal vesicles, spermatic cords, deferent ducts (vas deferens), ejaculatory ducts and the urethra.

Commonly Asked Questions:

  1. Enlist different body cavities along with their locations.

  2. Write in short about,

    1. Thoracic Cavity.

    2. Abdominal Cavity.

    3. Pelvic Cavity.
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