Body Structure and Function

Cell membrane

The outer covering of the cell.

Nucleus

The control center of the cell.

Cytoplasm

The substance that surrounds the nucleus.

Protoplasm

Refers to all structures, substances, and water within the cell.

Chromosomes

Thread-like structures in the nucleus containing genes.

Genes

Control the traits children inherit from their parents.

Epithelial tissue

Covers internal and external body surfaces.

Connective tissue

Anchors, connects, and supports other tissues.

Muscle tissue

Stretches and contracts to let the body move.

Nerve tissue

Receives and carries impulses to the brain and back to body parts.

Organs

Groups of tissue with the same function.

Systems

Formed by organs that work together to perform special functions.

Epidermis

The outer layer of the skin.

Dermis

The inner layer of the skin.

Subcutaneous tissue

Supports both the epidermis and the dermis.

Sweat glands

Help the body regulate temperature.

Oil glands

Lie near hair shafts and keep hair and skin soft and shiny.

Long bones

Bear the body's weight.

Short bones

Allow skill and ease in movement.

Flat bones

Protect the body's organs.

Irregular bones

Vertebrae in the spinal column.

Periosteum

The membrane covering bones.

Bone marrow

Found inside hollow centers of bones; forms blood cells.

Joint

The point at which two or more bones meet.

Ball-and-socket joint

Allows movement in all directions.

Hinge joint

Allows movement in one direction.

Pivot joint

Allows turning from side to side.

Voluntary muscles

Muscles that can be consciously controlled.

Involuntary muscles

Muscles that work automatically.

Central nervous system (CNS)

Consists of the brain and spinal cord.

Peripheral nervous system

Involves the nerves throughout the body.

Cerebrum

The center of thought and intelligence in the brain.

Cerebellum

Regulates and coordinates body movements.

Brainstem

Connects the cerebrum to the spinal cord and contains the midbrain, pons, and medulla.

Meninges

Three layers of connective tissue covering and protecting the brain and spinal cord.

Cerebrospinal fluid

Fluid that cushions shocks to the brain and spinal cord.

Plasma

Mostly water; carries blood cells and necessary substances to body cells.

Red blood cells (RBCs)

Called erythrocytes; contain hemoglobin and give blood its red color.

White blood cells (WBCs)

Called leukocytes; protect the body against infection.

Platelets

Also called thrombocytes; needed for blood clotting.

Pericardium

The outer layer of the heart.

Myocardium

The second (middle) layer of the heart.

Endocardium

The inner layer of the heart.

Atria

The two upper chambers of the heart that receive blood.

Ventricles

The two lower chambers of the heart that pump blood.

Diastole

The resting phase of heart action.

Systole

The working phase of heart action.

Arteries

Blood vessels that carry blood away from the heart.

Veins

Blood vessels that return blood to the heart.

Spleen

The largest structure in the lymphatic system; filters bacteria, destroys old RBCs, and stores blood.

Alveoli

Tiny air sacs in the lungs where gas exchange occurs.

Diaphragm

A muscle separating the lungs from the abdominal cavity.

Pleura

A two-layered sac covering each lung.

Alimentary canal

The GI tract extending from the mouth to the anus.

Peristalsis

Wavelike muscle contractions that push food through the alimentary canal.

Chyme

A semi-liquid substance formed by food mixed with gastric juices in the stomach.

Nephrons

Over a million tiny basic working units inside each kidney.

Ureters

Tubes that carry urine from the kidneys to the bladder.

Urethra

Tube that passes urine from the bladder out of the body.

Testes

Male sex glands (gonads) that produce sperm cells and testosterone.

Ovaries

Female gonads that contain ova and secrete estrogen and progesterone.

Fallopian tube

Tube through which an ovum travels from the ovary to the uterus.

Fertilization

The uniting of a sperm and ovum into one cell.

Pituitary gland

The master gland of the endocrine system, located at the base of the brain.

Thyroid gland

Butterfly-shaped gland in the neck that secretes thyroid hormone (thyroxine).

Adrenal glands

Glands located on top of each kidney that secrete hormones like epinephrine and cortisol.

Immunity

Protection against a specific disease or condition.