ALVEOLUS (plural, ALVEOLI)—a tiny air-filled sac within the lungs, the site at which gas exchange takes place and air from the lungs moves into the bloodstream. In the mandible, an alveolus is a tooth socket.
ANASTOMOSIS—a coming together of two completely separate blood vessels that ensures areas in the body are covered by blood arriving from multiple sources.
ANEURYSM—a weakened area in a blood vessel that bulges out and looks like a balloon. Aneurysms can occur anywhere in the body but can be particularly catastrophic if they burst either in the brain (brain aneurysm) or in the aorta (aortic aneurysm).
ANESTHESIA—in clinical practice, this refers to artificially numbing part of the body to pain, usually with intravenous drugs but sometimes also with drugs injected into the space around the spinal cord, or into the skin for a more localized effect.
APONEUROSIS—a flattened sheet of tendon connecting muscles.
AXON—the extension of a nerve cell (neuron) along which impulses travel from the cell body of one cell to other cells. They are long and wiry.
BILE—a yellow-green-brown fluid produced by the liver that breaks down fatty substances in food. It is stored and concentrated in the gallbladder.
BILIRUBIN—a yellow-orange substance formed by the breaking down of blood cells (hemoglobin). Accumulation of it in the blood and tissues gives the yellowy appearance of jaundice in the skin and sclera of the eye.
CAPILLARY—hair-thin (one-cell-thick) branching blood vessel that unites with other vessels to form a network between arterioles (medium-caliber oxygenated-blood-carrying vessels) and venules (medium-caliber deoxygenated-blood-carrying vessels). Gas exchange occurs in capillary beds.
CARTILAGE—a firm but flexible material found in several structures (external ear, larynx, respiratory tract, joints) giving them shape and the ability to move slightly. Most of the skeleton is cartilage in embryonic and fetal life but becomes bony at various stages in growth.
CELL—microscopic structures in the body, the smallest and most basic unit of living matter in an organism. Each cell is surrounded by a cell membrane, and contains genes, a nucleus, a fluid that enables chemical reactions (cytoplasm), and organelles (small structures with specialized functions).
CILIA (singular, CILIUM)—minuscule hair-like projections on cells that can move particles along. In the respiratory tract, they sweep together and push away fluid and particles.
CEREBROSPINAL FLUID (abbreviated to CSF)—clear fluid bathing the brain and spinal cord, acting as a shock absorber, lightening the weight of the brain and supplying it with nutrients. CSF is continuously produced and absorbed by the body.
CERVICAL (Latin, CERVIX means neck)—anything referring to the neck, either in the neck region between the head and trunk (as in cervical vertebra) or the cervix of the uterus (the narrow neck of the uterus at the upper end of the vagina that opens and widens during childbirth).
COMPARTMENT—anatomical or fascial compartments within the body that are surrounded by fascia and contain a group of muscles with a functionally similar action (for instance, biceps and triceps in the arm) as well as their blood and nerve supply.
CONNECTIVE TISSUE—tissues in the body that bind, support, separate, or connect structures (for instance, bones, ligaments, tendons, blood vessels, and cartilage). They have very few cells and are embedded in a matrix without cells (extracellular).
DIABETES—a common disease where the body is less able to respond to the hormone insulin or produce this hormone, resulting in high levels of glucose in the blood (normally glucose is mopped up from the blood by insulin). Two main types, Type 1 and Type 2.
DIALYSIS—a machine used to purify blood in a similar way to the kidneys and used in patients who have kidney damage. Prevents toxins and waste products from accumulating in the bloodstream.
DEOXYRIBONUCLEIC ACID (abbreviated to DNA)—present in most organisms, a self-replicating material. In living cells, DNA is found in chromosomes and contains our genetic instructions when linked together (gene).
DUCT—a tube that normally carries a secretion from a gland (for instance, the parotid duct carries saliva from the parotid gland into the mouth).
EMBRYOLOGICAL—refers to the earliest period within the development of the unborn individual. An embryo starts its life at fertilization (when an ovum and a sperm unite) until it is eight weeks old. After this stage, the embryo becomes a fetus.
ENDOCRINE—refers to glands that secrete hormones straight into the blood. Exocrine glands secrete their products via ducts (and not directly into the blood).
FASCIA (plural, FASCIAE)—a thin sheath (or sometimes layers) of fibrous tissue that surrounds muscles, organs, and vessels.
FISSURE—usually a naturally occurring groove or cleft in an organ or between body parts. Fissures are found on the brain and in the lungs.
FETUS—refers to the growing unborn human from week 8 after conception until birth. This is the stage when distinctly human features start to take shape.
FORAMEN—(plural, FORAMINA) any naturally-occurring openings or passages in the body, usually through a bone or into a bone.
FOSSA (plural, FOSSAE)—any shallow pit, cavity, or depression in a bone.
FRACTURE—a break in the continuity of a bone or cartilage (or the like). These usually need to be realigned so healing can occur.
FUNDOSCOPE (also known as OPHTHALMOSCOPE)—used to inspect the inside of the eye (fundus of the eye). Best utilized in a dark room when an eye drop has widened the pupil.
GANGLION (plural, GANGLIA)—a swelling on a nerve fiber with lots of nerve cell bodies within it, occurring outside the central nervous system.
GENITALIA—referring to the organs of reproduction (genitals) but mainly to those occurring externally.
GLAND—a group of cells that are specialized in function to do a particular job. Their main purpose is to produce chemical substances. Exocrine glands secrete their products via ducts (and not directly into the blood), while endocrine glands release products directly into the bloodstream for transportation to a distant site.
HERNIA—organs or fatty tissue can squeeze through weak areas in muscle walls or fascia. If they cannot go back to where they were intended to be, they may get trapped and the blood supply cut off.
HORMONE—chemical substance that regulates the way the body works, functioning like a complex signaling service. Normally, hormones are produced in specialized cells in glands and transported via the bloodstream to an organ or part of the body at a distant site.
INSERTION—muscles insert and originate at different places. The insertion of a muscle is where it is anchored on the bone, usually further away from the torso. When a muscle contracts, the insertion of the muscle is what moves the structure it is attached to.
JOINT—bones meet at junctions throughout the skeleton and are fitted together in a number of ways, some allowing movement and some not allowing movement. They are generally grouped together based on the type of movement allowed at the joint.
LACRIMAL—relates to the gland on the outer edge of the upper eyelid, which secretes a watery substance that helps to form tears and the tear film covering the eye. Lacrimation is the flow of tears.
LIGAMENT—bones are held together by tough but flexible bands of fibrous connective tissue and are similar to tendons. Although flexible, they do not stretch. Sometimes ligament also indicates structures that support or connect organs (there are several holding the uterus in place and others on the liver, for instance).
MAMMARY (Latin, MAMMA, probably a child’s first word for mother)—relates to breasts in females. These are milk-secreting glands from which babies receive their nourishment in infancy.
MASTICATORY—refers to the process of chewing and grinding food by the teeth and using muscles that do this in the head region, the masticatory muscles (there are four).
MATRIX (plural, MATRICES)—cells of connective tissue are embedded within a meshwork of material outside the cells (extracellular). Matrices are very variable in consistency—fluid in blood, firm and tough in cartilage, and hard in bone.
MEMBRANE—in gross anatomy, membranes are very thin pliable sheets of tissue that cover surfaces or enclose structures. The lungs, heart, brain, and some internal organs are enclosed within layers of membrane (pleura, pericardium, meninges, and peritoneum).
MIMETIC—mimetic muscles are a group of muscles in the face that are used to express emotions (for example, smiling or frowning). Also known as facial muscles or muscles of facial expression.
NERVE—white fibrous and wiry structures that transmit signals to the brain from muscles or organs. Nerves are enclosed in a cable-like sheath that protects the axons within. Afferent nerves carry sensation (touch, sound, etc.) to the central nervous system, and efferent nerves convey signals from the central nervous system to muscles or glands or organs. Some have a mixed function.
ORGAN—a self-contained part of an organism which usually has a specific function. Organs are formed by a group of tissues coming together to do a specific job or jobs.
ORIGIN—the place where a muscle starts on a bone, usually closer to the trunk than the peripheries, and this is a fixed attachment on a bone. The muscle has more bulk at its origin than at its insertion (where it attaches away from the torso).
ORGANISM—a form of life that is considered an entity but consists of interdependent parts that work together to sustain life. Humans are organisms (as are animals, plants, fungi, viruses, etc.). Organisms grow, reproduce, react to stimuli, and maintain a balance in the body (homeostasis).
PERINEAL—relating to the perineum, a diamond-shaped area below the pelvic diaphragm (a sheet of muscles separating pelvis and perineum) and between the thighs (between the vulva and the anus in women and between the scrotum and anus in men). It is an erogenous zone in both sexes.
PLAQUE—in medicine, these refer to clumps of cholesterol and other substances that stick on the inside of vessels and narrow the available space for blood to flow through. If they block the vessel, the area supplied by the artery becomes starved of blood. This is what happens in a heart attack or stroke.
PLASMA—clear and colorless fluid, essentially blood without platelets or red and white cells.
PLEXUS—an intricate web-like network of blood vessels, lymphatic vessels, or nerves in the body, the arrangement of which is usually complex. For instance, the brachial plexus is a bundle of nerves beginning at the base of the neck but becoming a tangle of closely connected nerves, with overlapping regions, and extending into the armpit to supply the entire upper limb.
POTENTIAL SPACE—these are spaces in the body between two structures that, normally, are closely pressed together, and are not real physical spaces. They have the potential to become spaces in disease, when they are filled with fluid or air, such as when air fills the space between two tightly pressed-together layers surrounding the lungs.
PREMATURE—a premature baby is born before 37 weeks of gestation, sometimes much earlier, which can be associated with risks of complications. The normal duration of gestation in humans is around 40 weeks, although delivery anywhere between 37 and 42 weeks is considered normal.
PROLAPSE—when an organ slips out of its normal place due to weakening of the supporting structures. Commonly occurs with the uterus, vagina, and bladder, but other organs can also prolapse.
REFLEX—involuntary actions by the nervous system to a stimulus. They cannot be controlled or overridden by conscious thought.
RETINA—the light-sensitive area at the back of the eye. Light is focused onto the retina via the lens, and impulses created on the retina are sent via the optic nerve for processing at the back of the brain (in the occipital lobe).
SINUS—usually a cavity within a bone, especially within the bones of the face. The paranasal sinuses in the facial skeleton are air-filled cavities lined with respiratory mucosa.
SPHINCTER—a ring of muscle that opens and closes tightly to allow substances to pass through at a desired pace or to guard an area. They are numerous in the body.
TENDON—cordlike band of fibrous tissue that connects a muscle to a bone (mainly). They are tough and do not stretch.
TISSUE—a group of cells with a similar structure that are woven together in an extracellular matrix to work together for a specific task. Organs are comprised of many groups of tissues working together.