Anatomy and Physiology: Body Structure, Function, and Organization

Anatomy

The study of the structure and shape of the body and its parts.

Physiology

The study of how the body and its parts work or function.

Gross Anatomy

Study of large, easily observable body structures with the naked eye.

Microscopic Anatomy

Study of body structures that cannot be seen without a microscope (e.g., histology, cytology).

Cytology

The microscopic study of individual cells.

Histology

The microscopic study of tissues and their structures.

Levels of Structural Organization

Chemical, Cellular, Tissue, Organ, Organ System, Organismal.

Chemical Level

Atoms combine to form molecules such as proteins, lipids, carbohydrates, and nucleic acids.

Cellular Level

Molecules associate to form cells, the fundamental structural and functional units of life.

Tissue Level

Groups of similar cells that have a common function.

Organ Level

Structures composed of two or more tissue types that perform specific, complex functions.

Organ System Level

A group of organs that work together to accomplish a common purpose.

Organismal Level

The highest level of structural organization, representing the total living human body.

Integumentary System

Skin, hair, nails, and sweat glands; protects underlying tissues, regulates body temperature, and synthesizes Vitamin D.

Skeletal System

Bones, cartilages, ligaments, and joints; provides framework, protects organs, allows movement, and stores minerals.

Muscular System

Skeletal muscles; contracts to produce movement, maintain posture, and produce body heat.

Nervous System

Brain, spinal cord, nerves, and sensory receptors; fast-acting control system that responds to internal and external changes.

Endocrine System

Glands that secrete hormones (e.g., pituitary, thyroid, adrenal); slow-acting control system regulating growth, metabolism, and reproduction.

Cardiovascular System

Heart and blood vessels; pumps blood to transport oxygen, carbon dioxide, nutrients, and wastes throughout the body.

Lymphatic System

Lymph nodes, lymphatic vessels, thymus, and spleen; picks up leaked fluid, returns it to blood, and houses immune cells.

Respiratory System

Nasal cavity, pharynx, larynx, trachea, bronchi, and lungs; keeps blood supplied with oxygen and removes carbon dioxide.

Digestive System

Oral cavity, esophagus, stomach, intestines, liver, and pancreas; breaks down food into absorbable units and eliminates indigestible wastes.

Urinary System

Kidneys, ureters, urinary bladder, and urethra; eliminates nitrogenous wastes and regulates water, electrolyte, and acid-base balance.

Reproductive System

Testes/Ovaries and associated structures; primary function is the production of offspring.

Homeostasis

The ability of the body to maintain a relatively stable internal environment despite continuous external changes.

Receptor (Sensor)

Sensor that monitors the environment and responds to stimuli by sending input along an afferent pathway.

Control Center

Analyzes input from receptor, determines set point, and sends output along an efferent pathway to the effector.

Effector

Provides the means for the control center's response (output) to the stimulus.

Negative Feedback System

Mechanism that reduces or shuts off the original stimulus to maintain dynamic equilibrium (e.g., body temperature, blood glucose).

Positive Feedback System

Mechanism that enhances or exaggerates the original stimulus, pushing the variable further from its initial state (e.g., blood clotting, labor contractions).

Anatomical Position

Standard body position: body erect, feet slightly apart, palms facing forward with thumbs pointing away from the body.

Superior (Cranial)

Toward the head end or upper part of a structure; above.

Inferior (Caudal)

Away from the head end or toward the lower part of a structure; below.

Anterior (Ventral)

Toward or at the front of the body; in front of.

Posterior (Dorsal)

Toward or at the back of the body; behind.

Medial

Toward or at the midline of the body; on the inner side of.

Lateral

Away from the midline of the body; on the outer side of.

Intermediate

Between a more medial and a more lateral structure.

Proximal

Closer to the origin of the body part or the point of attachment of a limb to the body trunk.

Distal

Farther from the origin of a body part or the point of attachment of a limb to the body trunk.

Superficial (External)

Toward or at the body surface.

Deep (Internal)

Away from the body surface; more internal.

Axial Region

Head, neck, and trunk portion of the body.

Appendicular Region

Limbs (arms and legs) attached to the body's axis.

Sagittal Plane

Vertical plane that divides the body into right and left parts.

Midsagittal (Median) Plane

Sagittal plane that lies exactly in the midline, dividing the body into equal right and left halves.

Parasagittal Plane

Sagittal plane offset from the midline, dividing the body into unequal right and left parts.

Frontal (Coronal) Plane

Vertical plane that divides the body into anterior (front) and posterior (back) portions.

Transverse (Horizontal) Plane

Horizontal plane running from right to left, dividing the body into superior (upper) and inferior (lower) portions.

Oblique Section

Cut made diagonally between horizontal and vertical planes.

Dorsal Body Cavity

Protects nervous system organs; subdivided into cranial cavity (brain) and vertebral/spinal cavity (spinal cord).

Ventral Body Cavity

Larger cavity housing internal organs (viscera); subdivided into thoracic cavity and abdominopelvic cavity.

Thoracic Cavity

Superior ventral cavity surrounded by ribs and chest muscles; contains pleural cavities and mediastinum.

Pleural Cavity

Subdivision of thoracic cavity, each enveloping a single lung.

Mediastinum

Central region of thoracic cavity containing the pericardial cavity (heart), esophagus, and trachea.

Pericardial Cavity

Encloses the heart within the mediastinum.

Abdominopelvic Cavity

Inferior ventral cavity separated from thoracic cavity by the diaphragm; divided into abdominal and pelvic cavities.

Abdominal Cavity

Contains stomach, intestines, spleen, liver, and other digestive organs.

Pelvic Cavity

Inferior part of abdominopelvic cavity containing urinary bladder, reproductive organs, and rectum.

Serous Membrane (Serosa)

Thin, double-layered membrane lining closed ventral body cavities and covering organs within them.

Parietal Serosa

Line cavity walls.

Visceral Serosa

Covers external surface of organs within cavities.

Serous Fluid

Lubricating fluid secreted by serous membranes to reduce friction between organs and cavity walls.

RUQ (Right Upper Quadrant)

Contains liver, gallbladder, duodenum, head of pancreas, right kidney, hepatic flexure of colon.

LUQ (Left Upper Quadrant)

Contains stomach, spleen, left lobe of liver, body of pancreas, left kidney, splenic flexure of colon.

RLQ (Right Lower Quadrant)

Contains cecum, appendix, ascending colon, right ovary, right fallopian tube, right ureter.

LLQ (Left Lower Quadrant)

Contains sigmoid colon, descending colon, left ovary, left fallopian tube, left ureter.

Plasma Membrane

Phospholipid bilayer with embedded proteins; selectively permeable barrier surrounding the cell.

Phospholipid Bilayer

Double layer of phospholipids with hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.

Passive Transport

Movement of substances across a membrane without energy expenditure (e.g., simple diffusion, facilitated diffusion, osmosis).

Simple Diffusion

Passive movement of unassisted solute particles from high to low concentration.

Facilitated Diffusion

Passive movement of molecules across a membrane with the aid of transmembrane proteins (channels/carriers).

Osmosis

Diffusion of water across a selectively permeable membrane from lower solute concentration to higher solute concentration.

Tonicity

The ability of an extracellular solution to make water move into or out of a cell by osmosis.

Isotonic Solution

Equal solute concentration inside and outside the cell; no net water movement.

Hypertonic Solution

Higher solute concentration outside the cell; causes cell to lose water and shrink (crenation).

Hypotonic Solution

Lower solute concentration outside the cell; causes cell to gain water and swell/burst (lysis).

Active Transport

Movement of substances against their concentration gradient (low to high) requiring energy (ATP).

Primary Active Transport

Directly uses energy from ATP hydrolysis to transport molecules (e.g., Na+/K+ ATPase pump).

Sodium-Potassium Pump (Na+/K+ ATPase)

Pumps 3 Na+ out of the cell and 2 K+ into the cell against concentration gradients using 1 ATP.

Endocytosis

Vesicular transport process that brings large substances or particles into the cell.

Phagocytosis

Cell eating; engulfment of large solid particles by pseudopods into a phagosome.

Pinocytosis

Cell drinking; non-specific ingestion of extracellular fluid and dissolved solutes.

Exocytosis

Process where intracellular vesicles fuse with the plasma membrane to secrete materials out of the cell.

Cytosol

Fluid portion of cytoplasm containing water, dissolved solutes, and proteins.

Mitochondria

Double-membraned organelle; site of aerobic cellular respiration and ATP synthesis (powerhouse of the cell).

Ribosomes

Dense granules of rRNA and protein; site of protein synthesis (translation).

Rough Endoplasmic Reticulum (RER)

Membranous network studded with ribosomes; modifies and packages proteins for secretion or membranes.

Smooth Endoplasmic Reticulum (SER)

Membranous network lacking ribosomes; synthesizes lipids, metabolizes carbohydrates, detoxifies drugs/toxins, stores Ca2+.

Golgi Apparatus

Stack of flattened membranous sacs; modifies, sorts, packages, and ships proteins from RER.

Lysosomes

Membrane-bound vesicles containing digestive enzymes (acid hydrolases); degrade foreign material and damaged organelles.

Peroxisomes

Membranous sacs containing oxidase and catalase enzymes; neutralize toxic free radicals and breakdown fatty acids.

Centrosome / Centrioles

Organizes microtubules and forms the mitotic spindle during cell division.

Nucleus

Control center of the cell containing genetic material (DNA).

Nuclear Envelope

Double-membrane barrier surrounding the nucleus with nuclear pores regulating traffic into/out of nucleus.

Nucleolus

Dense spherical body inside the nucleus; site of ribosomal RNA (rRNA) synthesis and ribosome assembly.

Chromatin

Threadlike complex of DNA and histone proteins found in non-dividing cells.

Interphase

Phase of cell cycle where cell grows, performs normal functions, and replicates DNA (subdivided into G1, S, G2).

Mitosis

Process of nuclear division in somatic cells resulting in two identical diploid daughter nuclei; consists of Prophase, Metaphase, Anaphase, Telophase.

Prophase

Chromatin condenses into chromosomes, nuclear envelope breaks down, mitotic spindle forms.