Body Regions and Anatomical Landmarks

Major Posterior Body Regions

The human body is divided into specific regions to facilitate anatomical study and medical reference. Posterior (back) regions are commonly identified by distinct anatomical landmarks.

• Occipital: Refers to the back of the head (A in Figure 1.1).

• Scapular: Pertains to the shoulder blade area (B in Figure 1.1).

• Acromial: The point of the shoulder (C in Figure 1.1).

• Lumbar: The lower back region, between the ribs and pelvis (D in Figure 1.1).

• Popliteal: The area behind the knee (E in Figure 1.1).

Example: The lumbar region is often associated with lower back pain due to its location and function in supporting body weight.

Directional Terms and Body Planes

Directional Terms

Directional terms are used to describe the locations of structures relative to other structures or locations in the body.

• Superior: Toward the head or upper part of a structure.

• Inferior: Away from the head or toward the lower part of a structure.

• Anterior (ventral): Toward the front of the body.

• Posterior (dorsal): Toward the back of the body.

• Medial: Toward the midline of the body.

• Lateral: Away from the midline of the body.

• Proximal: Closer to the origin of the body part or point of attachment.

• Distal: Farther from the origin of the body part or point of attachment.

Example: The wrist is distal to the elbow.

Body Planes

Body planes are imaginary lines that divide the body into sections for anatomical study.

• Transverse (horizontal) plane: Divides the body into superior and inferior parts.

• Coronal (frontal) plane: Divides the body into anterior and posterior parts.

• Sagittal plane: Divides the body into right and left parts. The midsagittal plane divides the body into equal right and left halves.

Example: A transverse plane could cut the head off the body.

Anatomical Position and Cavities

Anatomical Position

The anatomical position is a standard reference posture used in anatomy:

• Body is upright, facing forward.

• Feet are slightly apart.

• Arms are at the sides with palms facing forward (anteriorly).

Example: In anatomical position, the palms of the hands face medially toward the thighs.

Body Cavities

The body contains several cavities that house organs:

• Thoracic cavity: Contains the heart and lungs.

• Abdominal cavity: Contains digestive organs.

• Pelvic cavity: Contains reproductive organs, bladder, and rectum.

Example: The heart is located in the thoracic cavity.

Serous Membranes and Organ Systems

Serous Membranes

Serous membranes are thin tissues that line body cavities and cover organs. They secrete serous fluid to reduce friction.

• Function: Reduce friction so that viscera (internal organs) move freely.

• Contain air? Serous cavities do not contain air.

• Visceral serosa: Covers organs within the cavities.

• Parietal serosa: Lines the cavity walls.

Example: The lungs are covered by visceral pleura (a type of serous membrane).

Organ Systems

The body is organized into systems that perform specific functions.

• Integumentary system: Composed of skin, hair, and nails.

• Cardiovascular system: Includes the heart and blood vessels.

• Muscular system: Responsible for movement.

• Skeletal system: Provides support and protection.

Example: The skin is part of the integumentary system.

Levels of Organization and Biochemical Compounds

Levels of Organization

The human body is organized in a hierarchy from simplest to most complex:

• Chemical level: Atoms and molecules.

• Cellular level: Cells, the basic unit of life.

• Tissue level: Groups of similar cells performing a common function.

• Organ level: Structures composed of two or more tissue types.

• Organ system level: Groups of organs working together.

• Organismal level: The complete living being.

Example: A group of cells with similar structure and function is called a tissue.

Biochemical Compounds

There are four general types of biochemical compounds in the body:

• Carbohydrates: Building blocks are monosaccharides (simple sugars).

• Lipids: Building blocks are fatty acids and glycerol.

• Proteins: Building blocks are amino acids.

• Nucleic acids: Building blocks are nucleotides.

Example: DNA is a nucleic acid composed of nucleotide building blocks.

Key Anatomical Terms and Definitions

Definitions

• Physiology: The study of the function of body parts and how they work together.

• Anatomy: The study of the structure of body parts and their relationships.

• Axillary: Refers to the armpit region.

• Perineal: The region between the genitals and the anus.

Sample Table: Directional Terms Comparison

The following table compares common directional terms used in anatomy:

Additional info:

• Developmental anatomy studies the structural changes that occur as one ages.

• Regional anatomy focuses on specific areas of the body.

• Surface anatomy refers to the study of external features.

• Pathological anatomy studies disease-related changes.