Chapter 1
Organization of the Human Body –
Body Cavities and Membranes
Major Parts of Human Body
• The human body consists of three major
parts:
– Cavities
– Membranes
– Organ Systems
Major Divisions of the Human Body
• The human body can be separated into:
– Axial portion
• Includes the head, neck, and trunk
– Appendicular portion
• Includes the upper and lower limbs
Cavities of the Axial Portion
• Cranial cavity
– Houses the brain
Cavities of the Axial Portion
• Vertebral canal
– Contains the spinal cord surrounded by portions
of the backbone (vertebrae)
Cavities of the Axial Portion
• Thoracic cavity
– Contains organs called viscera:
• Lungs, heart, esophagus, trachea, and thymus gland
– The wall of the thoracic cavity consists of skin,
skeletal muscles, and bones.
– The region between the left and the right lungs is
called the mediastinum.
• The mediastinum contains the heart, esophagus,
trachea, and thymus gland
• Separates the thorax into two compartments (one
containing the right lung and one containing the left
lung).
Cavities of the Axial Portion
• Abdomino-pelvic cavity
– Includes an upper abdominal portion and a lower pelvic
portion
– Contains organs called viscera
• The viscera within the abdominal cavity include the stomach, liver,
spleen, gallbladder, and the small and large intestines
• The pelvic cavity (which is the area enclosed by the pelvic bones)
contains the terminal end of the large intestine, the urinary
bladder, and the internal reproductive organs
– The wall of the abdomino-pelvic cavity primarily consists of
skin, skeletal muscles, and bones
– Separated from the thoracic cavity by the diaphragm
• The diaphragm is a broad thin muscle that curves upward into the
thorax like a dome when it is at rest and presses down on the
abdominal viscera when it contracts during inhalation
Cavities of the Axial Portion
• Smaller cavities within the head:
– Oral cavity
• Contains the teeth and tongue
– Nasal cavity
• Located within the nose
• Divided into right and left portion by a nasal septum
• Several air-filled sinuses (including sphenoidal and frontal
sinuses) are connected to the nasal cavity.
– Orbital cavities
• Contain the eyes and associated muscles and nerves
– Middle ear cavities
• Contain the middle ear bones
Cavities of the Axial Portion
Cavities of the Axial Portion
Cavities of the Axial Portion
Thoracic and Abdominopelvic Membranes
• Serous membranes
– Thin membranes that line the walls of the thoracic
and abdominal cavities
– Fold back to cover organs within both cavities
– Secrete a slippery serous fluid that separates the
layer lining the wall (called the parietal layer) from
the layer covering the organ (called the visceral
layer)
Thoracic and Abdominopelvic Membranes
• Thoracic membranes
– Parietal pleura – serous membrane that lines the
right and left thoracic compartments, which
contain the lungs
– Visceral pleura – part of the parietal pleura that
folds back to cover the lungs
• A thin film of serous fluid separates the parietal and
visceral pleural membranes.
– Pleural cavity
• The potential space between the membranes
Thoracic and Abdominopelvic Membranes
• Pericardial membranes
– Surround the heart (which is located in the
broadest portion of the mediastinum)
• Visceral pericardium
– Cover’s the surface of the heart
• Parietal pericardium
– Layer that covers the visceral pericardium but that is
separated from the visceral pericardium by a small amount of
serous fluid.
» The potential space between the two membranes is
called the pericardial cavity
• Fibrous pericardium
– Much thicker layer that covers the parietal pericardium
Thoracic and Abdominopelvic Membranes
Thoracic and Abdominopelvic Membranes
• Abdominopelvic membranes
– Peritoneal membranes
• Parietal peritoneum
– Lines the wall
• Visceral peritoneum
– Covers each organ in the abdominal cavity
• Peritoneal cavity
– The potential space between the parietal peritoneum and the
visceral peritoneum
Thoracic and Abdominopelvic Membranes