Body Cavities

What is a body cavity?

•By the broadest definition, a body cavity is any fluid-filled space in a multicellular organism.

Body Cavities

• Usually refers to the space located between an animal’s outer covering (epidermis) and the outer lining of the gut cavity, where internal organs develop.

• "The body cavity" of the human usuallyrefers to the ventral body cavities, although there are other cavities as well.

The Ventral Body Cavities

Which is the ventral side of the human body?

The Ventral Body Cavity

• Contains all visceral organs within the abdomen and chest

• Substantially larger than the dorsal cavity

• Subdivided into the thoracic cavity and the abdominopelvic cavity The abdominopelvic cavity

is further divided into the abdominal and pelvic cavities

Thoracic Cavity

• Separated from the rest of the ventral cavity by the diaphragm

• The organs in the thoracic cavity are protected by the rib cage, and is lined by a membrane called the mesothelium

• What organs and structures does the thoracic cavity include?

The Mediastinum

• The thoracic cavity is separated by a central region called the mediastinum, which divides the lungs into left and right cavities

• The mediastinum houses the heart, trachea, esophagus, thymus, and other organs

Abdominal Cavity

•Below or __________ to the diaphragm

•Lined by a membrane called the peritoneum

•What organs does the abdominal cavity contain?

Further Divisions of the Abdominopelvic Cavity

Pelvic Cavity

• Inferior to the abdominal cavity

• Not continuous with the abdominal cavity in a straight plane, but instead, it tips off in a posterior direction

• Not separated by any physical structure from abdominal cavity

• Contains the reproductive organs, bladder, and rectum

The Dorsal Body Cavities

•Subdivided into the cranial and spinal cavities

•These cavities are continuous with one another

•The system of membranes that envelopes the central nervous system is called the meninges

•Cranial houses the brain•Spinal houses the spinal cord

Development of the Dorsal and Ventral

CavitiesThree germ cell layers correlate to anatomical development:Ectoderm (outermost: brain, spinal cord) gives rise to structures in the dorsal cavityEndoderm (innermost: lungs, liver, pancreas, bladder, stomach) andMesoderm (middle: heart, smooth muscle in gut, kidney) give rise to structures in the ventral cavity

Open Body Cavities

• Oral and Digestive Cavity

• Nasal Cavity

• Orbital Cavity

• Middle Ear Cavity

Oral and Digestive Cavity

• Oral cavity contains the teeth, tongue, and associated structures

• Continuous with the digestive cavity, which opens to the exterior at the anus

Nasal Cavity

Orbital Cavities

• House the eyes and present them in an anterior position

Middle Ear Cavities

• Lie medial to the eardrums

• Contain tiny bones that transmit sound to receptors in the inner ear

Quick Review

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