internal systems

Amino acid

Building blocks of proteins, containing an amino group, a carboxyl group, and a variable side chain.

Macromolecule

Large molecules, such as carbohydrates, proteins, lipids, and nucleic acids, essential for biological functions.

Monosaccharide

The simplest form of carbohydrates, consisting of a single sugar molecule.

Disaccharide

A carbohydrate composed of two monosaccharides joined by a glycosidic bond.

Polysaccharide

Carbohydrates that are made up of more than two monosaccharide units.

Peptide bond

The chemical bond formed between two amino acids during protein synthesis.

Dehydration synthesis

A chemical reaction that involves the combination of molecules with the removal of water.

Saturated fatty acid

A type of fatty acid that has no double bonds between carbon atoms, solid at room temperature.

Unsaturated fatty acid

A fatty acid that contains one or more double bonds, usually liquid at room temperature.

Triglyceride

A type of fat molecule made of glycerol and three fatty acids, used for energy storage.

Primary structure

The sequence of amino acids in a protein chain.

Secondary structure

The folding or coiling of the protein chain into alpha helices or beta sheets.

Tertiary structure

The overall three-dimensional shape of a protein, determined by interactions among side chains.

Quaternary structure

The structure formed when two or more protein chains combine.

Duodenum

The first section of the small intestine where most chemical digestion occurs.

Jejunum

The middle section of the small intestine where absorption of nutrients primarily occurs.

Ileum

The final section of the small intestine that connects to the large intestine.

Ileocaecal valve

The valve located between the ileum of the small intestine and the cecum of the large intestine.

Villi

Small, finger-like projections in the small intestine that increase surface area for absorption.

Microvilli

Tiny hair-like structures on the surface of villi that further increase absorption surface area.

Chyme

A semi-liquid mixture of food and digestive juices that passes from the stomach to the small intestine.

Peristalsis

The wave-like muscle contractions that move food through the digestive tract.

Cardiac sphincter

The muscular valve that controls the opening between the esophagus and the stomach.

Pyloric sphincter

The valve that controls the passage of chyme from the stomach to the small intestine.

Bolus

A mass of chewed food that is ready to be swallowed.

Smooth muscle

Involuntary muscle found in the walls of organs that contracts to facilitate movement.

Diaphragm

A dome-shaped muscle that separates the thoracic cavity from the abdominal cavity and aids in respiration.

Pleura

The membrane surrounding the lungs and lining the chest cavity.

Alveoli

Tiny air sacs in the lungs where gas exchange occurs.

Medulla oblongata

Part of the brain that regulates vital functions such as breathing and heart rate.

Intercostal muscles

Muscles located between the ribs that assist with breathing.

Tidal volume

The amount of air inhaled or exhaled during normal breathing.

Expiratory reserve volume

The volume of air that can be forcibly exhaled after a normal expiration.

Total lung capacity

The maximum amount of air the lungs can hold.

Inspiratory reserve volume

The amount of air that can be inhaled beyond a normal breath.

Vital capacity

The maximum amount of air that can be exhaled after a maximum inhalation.

Residual volume

The amount of air left in the lungs after maximum exhalation.

Plasma

The liquid component of blood that carries cells, nutrients, hormones, and waste.

Pericardium

The double-walled sac that encloses the heart.

Epicardium

The outer layer of the heart wall, also part of the pericardium.

Myocardium

The muscular middle layer of the heart wall responsible for contraction.

Endocardium

The inner layer of the heart that lines the chambers and valves.

Erythrocytes

Red blood cells responsible for transporting oxygen throughout the body.

Leucocytes

White blood cells that are part of the immune system and help defend against infection.

Platelets

Small cell fragments in the blood that are essential for clotting.

Hemoglobin

The protein in red blood cells that binds to and carries oxygen.

Fibrin

A protein that helps form blood clots during the coagulation process.

Homeostasis

The process by which biological systems maintain stability while adjusting to conditions.

Systole

The phase of the heartbeat when the heart muscle contracts and pumps blood.

Diastole

The phase of the heartbeat when the heart muscle relaxes and fills with blood.

Systolic pressure

The pressure in the arteries during the contraction of the heart.

Diastolic pressure

The pressure in the arteries when the heart is at rest between beats.