NOTE: Lecture notes are intended to help the student organize their notes and facilitate assimilation of the material. They are in no way a substitute for the actual lectures; however, this material will be covered on exams!
STRUCTURAL PLAN OF THE HUMAN BODY:
Humans are BILATERALLY SYMMETRICAL; in other words, the right & left sides of the body are mirror images of each other.
The human body's organization is a TUBE-WITHIN-A-TUBE construction. The outer tube is the body wall. The inside tube is the gastrointestinal (digestive) tract, which passes through the body from the mouth to the anus.
Humans have a VERTEBRAL COLUMN (backbone) and a CRANIUM (braincase). These characteristics put humans in the category of VERTEBRATES. Vertebrates include fish, amphibians, reptiles, birds, and mammals.
ANATOMICAL POSITION:
The anatomical reference point is a standard body position called the ANATOMICAL POSITION. Always assume that the body is in the anatomical position when describing where body parts are located. In the anatomical position, the body is standing upright, facing the observer. The feet are flat on the floor. The arms are hanging at the sides of the body. The palms face forward and the thumbs are pointed away from the body. The woman facing you in FIG. 1.2 is in the anatomical position.
Please learn the ANATOMICAL TERMS (except "sural" and "crural") for the different regions of the body (FIGURE 1.2). The anatomical terms are in parentheses. Note that some are on the anterior side and some are on the posterior side of the body.
DIRECTIONAL TERMS:
Anatomists and medical personnel use specific DIRECTIONAL TERMS to describe where body parts are located. Please refer to EXHIBIT 1.1 and FIG. 1.5 for further definitions and examples. Remember to always assume that the body is in the ANATOMICAL POSITION when describing where structures are located.
1. SUPERIOR: toward the head or the upper part of the body or structure; "above". Example: The nose is superior to the chin.
2. INFERIOR: toward the lower part of the body or structure; "below". Example: The mouth is inferior to the nose.
3. ANTERIOR (VENTRAL): toward or at the front of the body; "in front of". Example: The breastbone is anterior to the spine.
4. POSTERIOR (DORSAL): toward or at the back of the body; "behind". Example: The heart is posterior to the breastbone.
5. MEDIAL: toward or at the midline of the body or structure. (The midline is an imaginary vertical line that divides the body into equal right and left sides.) Example: The heart is medial to the lungs.
6. LATERAL: away from the midline of the body or structure. Example: The eyes are lateral to the bridge of the nose.
7. IPSILATERAL: on the same side of the body. Example: The left arm & left leg are ipsilateral.
8. CONTRALATERAL: on the opposite side of the body. Example: The left arm & right leg are contralateral.
9. PROXIMAL: closer to the point of attachment of a limb to the body trunk. Example: The elbow is proximal to the hand.
10. DISTAL: farther from the point of attachment of a limb to the body trunk. Example: The knee is distal to the thigh.
11. SUPERFICIAL: toward or at the body surface. Example: The skin is superficial to the skeleton.
12. DEEP: away from the body surface; more internal. Example: The lungs are deep to the ribs.
PLANES AND SECTIONS:
The study of anatomy often involves dissection, in which the body or its organs are SECTIONED (cut) along an imaginary flat surface called a PLANE. A SECTION is the exposed flat surface that results from the cut made through the body or organ. (So, the term "section" is used both as a verb and as a noun.) The most frequently used planes are the SAGITTAL, FRONTAL and TRANSVERSE planes. These planes lie at right angles to each other. See FIGS. 1.3 & 1.4 for examples of planes and sections:
1. A SAGITTAL PLANE is a vertical plane that divides the body or organ into right and left portions. A cut along a sagittal plane produces a SAGITTAL SECTION (a MIDSAGITTAL SECTION or a PARASAGITTAL SECTION – see below for definitions).
A. A MIDSAGITTAL PLANE is exactly at the midline of the body or organ, and divides the body or organ into equal right and left sides.
B. A vertical plane that divides the body or organ into unequal right and left sides is a PARASAGITTAL PLANE.
2. A vertical plane that divides the body or organ into anterior and posterior portions is a FRONTAL (CORONAL) PLANE. A cut made along a frontal plane produces a FRONTAL SECTION.
3. A TRANSVERSE (HORIZONTAL) PLANE runs parallel to the ground and divides the body into superior and inferior portions. A cut made along a horizontal plane produces a TRANSVERSE (HORIZONTAL) SECTION. The transverse section is also sometimes called a CROSS-SECTION.
BODY CAVITIES
Spaces within the body that contain internal organs are called BODY CAVITIES. See FIG. 1.6. The two principal body cavities are the DORSAL and VENTRAL body cavities.
1. The DORSAL BODY CAVITY is located near the posterior surface of the body. It is further subdivided into a CRANIAL CAVITY and a VERTEBRAL CANAL.
A. The CRANIAL CAVITY is a bony cavity formed by the skull. It contains the brain.
B. The VERTEBRAL CANAL is also called the SPINAL CANAL. It is a bony cavity formed by the vertebrae of the backbone. It contains the spinal cord. Since the spinal cord emerges from the brain, the cranial and vertebral cavities are continuous with one another.
2. The VENTRAL BODY CAVITY is located in the anterior part of the body. The ventral body cavity walls are made of skin, connective tissue, bone, and muscles. The organs inside the ventral body cavity are called the VISCERA. The ventral body cavity is further subdivided into the THORACIC and ABDOMINOPELVIC CAVITIES by the DIAPHRAGM, a large, dome-shaped muscle used in breathing.
A. The THORACIC CAVITY (see FIG. 1.7) is surrounded by the ribs and muscles of the chest. It is further subdivided into the two PLEURAL CAVITIES and the MEDIASTINUM. Each PLEURAL CAVITY contains one lung. The MEDIASTINUM is medial to the pleural cavities. The mediastinum is not a cavity. It is defined as a region or mass of tissue that extends from the breastbone (sternum) to the vertebral column. The mediastinum contains the PERICARDIAL CAVITY, which encloses the heart. The mediastinum also contains other thoracic organs & structures (for example: the thymus, aorta and esophagus).
B. The ABDOMINOPELVIC CAVITY (FIGS. 1.6 & 1.8) is inferior to the thoracic cavity and the diaphragm. The abdominopelvic cavity is subdivided into two portions, which are not separated by any physical partition. The superior portion is the ABDOMINAL CAVITY, which contains the stomach, small intestine, part of the large intestine, spleen, liver, gall bladder, and pancreas. The inferior part is the PELVIC CAVITY, which contains the urinary bladder, the internal male and female reproductive organs, and the lower part of the large intestine.
ABDOMINOPELVIC CAVITY REGIONS - see FIG. 1.9
1. The UMBILICAL REGION is deep to and surrounding the navel.
2. The EPIGASTRIC REGION is superior to the umbilical region.
3. The HYPOGASTRIC (pubic) REGION is inferior to the umbilical region.
4. The RIGHT and LEFT HYPOCHONDRIAC REGIONS are lateral to the epigastric region.
5. The RIGHT and LEFT LUMBAR REGIONS are lateral to the umbilical region.
6. The RIGHT and LEFT ILIAC (inguinal) REGIONS are lateral to the hypogastric region.
SEROUS MEMBRANE (pages 15 & 84, and FIG. 3.7, page 83)
The walls of the VENTRAL BODY CAVITY and the outer surfaces of the organs inside it are covered with an extremely thin tissue membrane called the SEROSA or SEROUS MEMBRANE. The serous membrane is an EPITHELIAL TISSUE MEMBRANE consisting of AREOLAR CONNECTIVE TISSUE covered by SIMPLE SQUAMOUS EPITHELIUM.
The serous membrane in the pleural (lung) cavity is called PLEURA. The serous membrane in the pericardial (heart) cavity is called PERICARDIUM. The serous membrane in the abdominopelvic cavity is called PERITONEUM. You will not be tested on these terms on Exam 1, but you will need to know these terms when we get to the respiratory, cardiovascular, and digestive systems.
The part of the serous membrane that lines the ventral body cavity walls is called the PARIETAL SEROSA. The parietal serosa is continuous with the VISCERAL SEROSA, which covers the organs (VISCERA) within the cavity. The POTENTIAL SPACE between the parietal and visceral serosa contains a thin lubricating fluid, called SEROUS FLUID, which reduces friction between organs within the body cavity.