Anatomy and Physiology: Organization, Terms, and Planes
1. Organelles, Cells, Tissues, Organs, Organ Systems
- Organelles: Small structures inside a cell that perform specific functions.
- Cells: The basic units of structure and function in living things.
- Tissues: Groups of similar cells and some extracellular material, organized to perform a function.
- Organs: Structures made of two or more tissues that perform a specialized function.
- Organ systems: Groups of organs that work together to perform a specialized function.
Order to memorize:
Organelles → cells → tissues → organs → organ systems → organism
2. Directional Terms
Superior / Inferior
Superior = toward the head; above.
Inferior = away from the head; below.
Anterior / Posterior
Anterior = toward the front of the body.
Posterior = toward the back of the body.
In humans, anterior is also called ventral. Posterior is also called dorsal.
Medial / Lateral / Intermediate
Medial = toward the body’s midline. Example: La nariz está medial a los ojos.
Lateral = away from the body’s midline. Example: Las orejas están laterales a la nariz.
Intermediate = between a medial and a lateral structure. Example: El dedo índice está entre el pulgar y el dedo medio.
Proximal / Distal
Proximal = closer to the point where a limb attaches to the body.
Distal = farther from the point where a limb attaches to the body.
Example: The elbow is proximal to the wrist. The wrist is distal to the elbow.
Superficial / Deep
Superficial = toward or at the body surface.
Deep = away from the body surface; more internal.
Example: The skin is superficial to the muscles. The muscles are deep to the skin.
3. Body Planes
- Sagittal plane: Divides the body into right and left parts.
- Midsagittal, or median, plane: Divides the body through the midline into equal right and left halves.
- Frontal, or coronal, plane: Divides the body into anterior and posterior parts.
- Transverse, or horizontal, plane: Divides the body into superior and inferior parts.
- Oblique section: A cut made diagonally.
Quick reminder: Sagittal = right and left. Frontal = front and back. Transverse = upper and lower. Oblique = diagonal.
4. Body Cavities and Membranes
Dorsal body cavity: The posterior cavity that protects the nervous system.
- Cranial cavity: Located within the skull; contains the brain.
- Vertebral, or spinal, cavity: Located within the vertebral column; contains the spinal cord.
Ventral body cavity: The anterior cavity that contains internal organs.
- Thoracic cavity: The chest cavity; contains the heart and lungs.
- Abdominopelvic cavity: Located below the diaphragm; divided into abdominal and pelvic cavities.
The Thoracic Cavity
- Pleural cavities: Surround the lungs, one cavity for each lung.
- Mediastinum: The region between the lungs.
- Pericardial cavity: Surrounds the heart and lies within the mediastinum.
The Abdominopelvic Cavity
- Abdominal cavity: Contains the stomach, intestines, liver, and other organs.
- Pelvic cavity: Contains the bladder, reproductive organs, and rectum.
- Diaphragm: The muscle that separates the thoracic cavity from the abdominopelvic cavity.
Serous Membranes
Thin membranes that secrete serous fluid to reduce friction between organs and cavity walls.
- Parietal serosa: Lines the internal body wall.
- Visceral serosa: Covers an internal organ.
- Serous fluid: The fluid between the parietal and visceral layers.
Membranes to match with each area:
- Pleura: Lungs.
- Pericardium: Heart.
- Peritoneum: Abdominopelvic organs.
Peritoneum: The parietal peritoneum lines the abdominopelvic wall. The visceral peritoneum covers each abdominal organ. The peritoneal cavity is the space between the two layers.
Other Body Cavities
- Oral cavity: The mouth.
- Nasal cavity: Located within the nose.
- Orbital cavities: House the eyes.
- Middle ear cavities: Contain small bones that transmit sound vibrations.
- Synovial cavities: Joint cavities.
5. Characteristics of Life
These definitions are copied from your notes:
- Absorption: “Passage of substances through membranes and into body”
- Assimilation: “Changing of absorbed substances into chemically different forms”
- Circulation: “Movement of substances in body fluids”
- Digestion: “Breakdown of food substances into simpler forms”
- Excretion: “Removal of wastes produced by metabolic reactions”
- Growth: “Increase in body size; no change in shape”
- Movement: “Change in position; motion”
- Reproduction: “Production of new organisms and new cells”
- Respiration: “Obtaining oxygen; removing carbon dioxide; releasing energy from foods”
- Responsiveness: “Reaction to change”