IB Bio Topic 6 (All Subtopics)

Assimilation

The process in which essential molecules from ingested food enter the bloodstream to be accessed by body cells for cellular activities.

Alimentary Canal (Digestive Tract)

Organs that form the “tube” of the digestive system.

Accessory Organ

In the digestive system, these types of organs secrete chemicals into the main tube of the system.

Pancreas

Secretes amylase, lipase, and protease into the small intestine.

Liver

Secretes bile to emulsify lipids (break them into smaller particles).

Gall Bladder

Stores bile.

Bile

a SUBSTANCE secreted by the liver. It is not an enzyme and does not hydrolyze any reactions.

Mouth

Where food is mechanically chewed and mixed with amylase-containing saliva; carbohydrate digestion begins

Bolus

mixture of food and saliva

Peristalsis

a wave of contraction and relaxation of the longitudinal and circular muscles along the alimentary canal, forcing contents through the tube

Chyme

mixture of bolus from the esophagus and stomach acid

Small Intestine

a long, muscular tube located between the stomach and large intestine in humans

Duodenum

first section of the small intestine

Jejunum

middle section of the small intestine

Ileum

last section of the small intestine

Serosa

outermost layer of the small intestine, has connective tissue that touches body cavities

Submucosa

connective tissue of the small intestine; supports mucosa, contains large veins & arteries that result in the mucosa’s capillary bed

Mucosa

innermost layer of the small intestine, forms soft lining of the tube, made of epithelium

Lumen

physical space in the center of intestines, arteries, and other tubular structures of the human body

Duct Cells

Cells from the pancreas that transport enzymes produced by acinar cells. They also secrete sodium hydrogen carbonate to neutralize stomach acid.

Acinar Cells

Cells from the pancreas that secrete digestive enzymes.

Amylase

an enzyme that breaks down starch into maltose

Endopeptidase (Trypsin)

an enzyme that breaks down proteins into smaller polypeptides

Lipase

enzymes that break down lipids into glycerol and fatty acid monomers

Phospholipase

enzymes that break down phospholipids into glycerol, fatty acid, and phosphate monomers

Nuclease

an enzyme that breaks down DNA and RNA

Maltase

an enzyme that breaks down maltose into glucose

Lactase

an enzyme that breaks down lactose into galactose and glucose

Exopeptidase

an enzyme that removes a single amino acid from the end of small peptides

Dipeptidase

an enzyme that breaks dipeptides into two amino acids

Absorption

The taking in of digested food substances, vitamins, and minerals from the lumen of the small intestine into the blood

Villi

specialized structures that cover the inner surface of the small intestine, increasing its surface area

Epithelial Cells

the cells in villi where absorption actually occurs

Goblet Cells

cells in villi that produce mucus

Lamina propia

connective tissue of the villus

Microvilli

projections of each epithelial cell of a villus. They further increase the surface area of the small intestine.

Lacteal

a structure within the villi of the digestive tract that connects to the lymph.

Maltose

a dimer made up of two glucose molecules linked by 𝝰-1,4 glycosidic bonds

Maltotriose

a trisaccharide made up of three glucose molecules linked by 𝝰-1,4 glycosidic bonds

Glucosidase

an enzyme that breaks down maltotriose

Dextrin

small polymers that contain 𝝰-1,6 glycosidic bonds. They are left over after amylopectin’s 𝝰-1,4 glycosidic bonds are broken up by amylase

Dextrinase

an enzyme that breaks down dextrin

Dialysis

the separation of smaller molecules from larger molecules in a solution by selective diffusion through a semipermeable membrane

Arteries

a type of blood vessel known for conveying blood at high pressures from the ventricles to the tissues of the body

Aorta

the main, largest artery of the heart, which connects it to the rest of the body

Systolic Pressure

refers to the part of the heartbeat when muscles are contracting

Diastolic Pressure

refers to the part of the heartbeat when muscles are relaxing

Arterial Walls (Walls of Arteries)

contain elastic fibers that stretch with heartbeats and recoil when the muscles relax, propelling blood forward. Also have muscular walls to help maintain blood pressure between pump cycles.

Tunica Intima

the innermost layer of the arterial wall; it is in direct contact with the blood in the lumen. The inner part that faces the lumen is lined with endothelium, which forms a smooth, friction-reducing lining

Tunica Media

the middle coat of the arterial wall. It is mainly made of smooth (involuntary) muscle cells and elastic fibers arranged in spiral layers. It is the thickest of the three layers

Tunica Adventitia

the outermost coat of the arterial wall. It is a tough layer of loosely woven collagen fibers that protect the blood vessel and anchor it to nearby structures

Vasoconstriction

the constriction of circular muscles surrounding arteries due to the constriction of the heart causing arteries to experience high pressure

Vasodilation

the relaxation of circular muscles surrounding arteries due to the relaxation of the heart causing arteries to experience low pressure

Arterioles

smaller arteries in the body that branch off to supply blood to organs, limbs, etc.

Heart Rate (Pulse)

The number of times the heart beats per minute

Stroke Volume

the volume of blood pumped out of the left ventricle of the heart during each contraction/heartbeat

Cardiac Output

the volume of blood pumped through the circulatory system in a minute

Atria

the upper tissues of the heart

Ventricles

the lower tissues of the heart

Veins

blood vessels that transport blood from the tissues of the body back to the heart (specifically the atria) at a low pressure

Plasma

the liquid portion of blood. It carries dissolved substances like CO2, hormones, vitamins, minerals, glucose, and proteins

Capillaries

very small blood vessels formed from the successive division of arterioles. They are only one cell thick and lack any other wall structure

Venules

small blood vessels that form veins when many of them fuse together

Tissue Fluid (Interstitial Fluid)

the liquid part of the blood that passes through capillary walls to bathe tissue cells

Double Circulatory System

refers to the fact that blood enters the heart twice before it is distributed to the tissues

Vena Cava

a large vein that carries blood back to the heart. There is a superior and inferior version of it.

Atrioventricular Valves

open and close to control the flow of blood from the atria to the ventricles on either side of the heart

Septum

the space separating the two sides of the heart

Pulmonary Artery

A type of artery that carries deoxygenated blood from the heart to the lungs

Pulmonary Vein

A type of vein that carries oxygenated blood from the lungs back to the heart

Sinoatrial Node (SA Node)

a group of specialized muscle cells in the wall of the right atrium of the heart. It is known as the “pacemaker” because it initiates heartbeats and sets the heart rate.

Cardiac Cycle

the complete sequence of events in the heart from the start of one beat to the beginning of the next.

Bundle of His

The signal emitted by the SA Node arrives here from the AV node. It is located in the interventricular septum.

Purkinje Fibers

The signal emitted by the SA Node passes through here to reach the ventricles.

Isovolumetric

refers to when a ventricle contracts or relaxes with no corresponding volume change. This occurs because valves are still closed

Cardiac Accelerator Nerve

a nerve located in the medulla oblongata of the brain (in a part of it called the cardiovascular center). It simulates the heart to beat faster

Vagus Nerve

another nerve located in the medulla oblongata. It stimulates the heart to beat slower

Cardiovascular Center

the part of the brain that monitors blood pressure, pH, and CO₂ concentrations to determine whether impulses to the heart should be propagated via the cardiac accelerator nerve or the vagus nerve

Epinephrine (Adrenaline)

the “fight or flight” hormone that is located in the medulla of the adrenal glands. It increases the heart rate by stimulating the SA node to initiate signals at a faster rate, as well as increasing the speed of the signals emitted by the SA and AV nodes

Atheromas

fatty deposits caused by high blood concentrations of low density lipoprotein (LDL) in the arterial walls next to endothelial cells

Thrombosis

the forming of a clot in a blood vessel that can block it entirely. These fatty deposits start as ruptures in the arterial walls, and can end up blocking the artery entirely

Coronary Artery

an artery that supplies the heart with oxygen and nutrients

Angina

medical term for the chest pain caused by the restricted flow of blood in a coronary artery (due to deprived oxygen and nutrients)

Skin

the outermost layer of the body. It notably has pores for sweating, hair follicles, and sebaceous glands that produce oils called sebum

Sebum

Oils that keep the skin supple and at a slightly lower pH, making it more difficult for pathogenic bacteria to live on the skin

Mucus Membranes

membranes made up of a surface layer of epithelial cells over a deeper layer of connective tissue. They produce mucus for protection and lubrication

Mucus

A sticky substance that contains glycoproteins and lysozymes (enzymes that attack bacterial cell walls), both of which have antiseptic properties

Clotting Factors

inactive proteins in the blood that are activated individually during a series of several reactions involved in forming blood clots.

Platelets

cell fragments that release chemicals to start the reactions required to form blood clots. They release clotting factors.

Fibrinogen

a soluble, inactive clotting factor in blood that is ultimately converted into fibrin

Fibrin

an insoluble molecule that fibrinogen is converted into by a reaction catalyzed by the enzyme thrombin

Thrombin

An enzyme that catalyzes the reaction that converts fibrinogen into fibrin

Scab

a protective layer formed after a network of fibrin traps red blood cells and platelets. It prevents the entry of pathogens into the exposed skin below it, which is allowed to heal

Thrombus

a blood clot that forms in a vessel and remains in the place where it was formed

Coronary Thrombus

a thrombus that forms in a coronary artery

Specific Immune System

The type of immune system that refers to lymphocytes and antibodies

Non-Specific Immune System

The type of immune system that refers to phagocytes

Leukocytes (White Blood Cells)

any blood cell that has immune function

Phagocytes (Macrophages)

leukocytes that (after chemically recognizing a pathogen) move by amoeboid motion to engulf pathogens and digest them via enzymes secreted from lysosomes

Pathogen

a disease-causing virus or microorganism (viruses, bacteria, protozoans, fungi, prions)