Animal Form and Function

Animal Body Planes and Cavities

A standing vertebrate animal can be divided by several planes. A sagittal plane divides the body into right and left portions. A midsagittal plane divides the body exactly in the middle, making two equal right and left halves. A frontal plane (also called a coronal plane) separates the front from the back. A transverse plane (or, horizontal plane) divides the animal into upper and lower portions. This is sometimes called a cross section, and, if the transverse cut is at an angle, it is called an oblique plane. Figure illustrates these planes on a goat (a four-legged animal) and a human being.

Illustration A shows the planes of a goat body. The midsagittal plane runs through the middle of the goat from front to back, separating the right and left sides. The frontal plane also runs from front to back, but separates the upper half of the body from the lower half. The transverse plane runs across the middle of the goat, and separate the front and back halves of the body. Illustration B shows the planes of a human body. The midsagittal plane runs from top to bottom and separates the right and left halves of the body. The Frontal plane also runs from top to bottom and separates the front and back halves of the body. The Transverse plane dissects the middle of the body between the chest and abdomen, separating the top of the body from the bottom. The midline is an imaginary line running through the middle of the body, from top to bottom.
Shown are the planes of a quadrupedal goat and a bipedal human. The midsagittal plane divides the body exactly in half, into right and left portions. The frontal plane divides the front and back, and the transverse plane divides the body into upper and lower portions.

Vertebrate animals have a number of defined body cavities, as illustrated in Figure. Two of these are major cavities that contain smaller cavities within them. The dorsal cavity contains the cranial and the vertebral (or spinal) cavities. The ventral cavity contains the thoracic cavity, which in turn contains the pleural cavity around the lungs and the pericardial cavity, which surrounds the heart. The ventral cavity also contains the abdominopelvic cavity, which can be separated into the abdominal and the pelvic cavities.

Illustration shows a cross-sectional side view of the upper part of a human body. The entire head region above the eyes and to the back of the head and a long thin strip from this region down the back is shaded to indicate the dorsal cavity. The head is labeled cranial cavity and the long thin region down the back is the spinal cavity. A large oblong area shaded at the front of the body indicates the ventral cavity. It is labeled from top to bottom as thoracic cavity, diaphragm (thin line separating regions), abdominal cavity, and pelvic cavity. The abdominal and pelvic cavities are separated by a thin dashed line and together they are labeled the abdominopelvic cavity.
Vertebrate animals have two major body cavities. The dorsal cavity, indicated in green, contains the cranial and the spinal cavity. The ventral cavity, indicated in yellow, contains the thoracic cavity and the abdominopelvic cavity. The thoracic cavity is separated from the abdominopelvic cavity by the diaphragm. The thoracic cavity is separated into the abdominal cavity and the pelvic cavity by an imaginary line parallel to the pelvis bones. (credit: modification of work by NCI)

Career Connections

Physical AnthropologistPhysical anthropologists study the adaption, variability, and evolution of human beings, plus their living and fossil relatives. They can work in a variety of settings, although most will have an academic appointment at a university, usually in an anthropology department or a biology, genetics, or zoology department.

Nonacademic positions are available in the automotive and aerospace industries where the focus is on human size, shape, and anatomy. Research by these professionals might range from studies of how the human body reacts to car crashes to exploring how to make seats more comfortable. Other nonacademic positions can be obtained in museums of natural history, anthropology, archaeology, or science and technology. These positions involve educating students from grade school through graduate school. Physical anthropologists serve as education coordinators, collection managers, writers for museum publications, and as administrators. Zoos employ these professionals, especially if they have an expertise in primate biology; they work in collection management and captive breeding programs for endangered species. Forensic science utilizes physical anthropology expertise in identifying human and animal remains, assisting in determining the cause of death, and for expert testimony in trials.