IB Biology - Human Physiology

Teeth

Teeth

Break down food into smaller pieces through chewing (mechanical digestion).

Salivary Glands

Produce saliva containing the enzyme amylase, which begins the breakdown of carbohydrates (chemical digestion).

Pharynx (Throat)

Passageway for food and air.

Esophagus

A muscular tube that connects the throat to the stomach, using peristalsis to move food.

Stomach

A muscular, J-shaped organ where food is mixed with gastric juices to begin the digestion of proteins.

Chyme

The semi-liquid mixture of partially digested food and gastric juices in the stomach.

Duodenum

The first section of the small intestine where chyme is mixed with bile and pancreatic juice.

Jejunum and Ileum

Sections of the small intestine where nutrient absorption occurs, lined with villi and microvilli.

Liver

Produces bile, which emulsifies fats to make them easier to digest.

Gallbladder

Stores bile and releases it into the duodenum.

Pancreas

Produces pancreatic juice containing digestive enzymes and bicarbonate to neutralize stomach acid.

Large Intestine (Colon)

Absorbs water and electrolytes from indigestible food residue, forming solid waste (feces).

Rectum

Stores feces until they are excreted.

Peristalsis

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

Anus

The opening at the end of the digestive tract where feces are expelled.

Bile

A digestive fluid produced by the liver and stored in the gallbladder, emulsifying fats.

Villi

Finger-like projections in the small intestine that increase the surface area for nutrient absorption.

Microvilli

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

Amylase

An enzyme in saliva and pancreatic juice that breaks down carbohydrates into simpler sugars.

Pepsin

An enzyme in the stomach that begins the digestion of proteins into smaller peptides.

Trypsin

An enzyme produced by the pancreas that further breaks down proteins in the small intestine.

Lipase

An enzyme produced by the pancreas that breaks down fats into fatty acids and glycerol.

Bicarbonate

A substance produced by the pancreas that neutralizes stomach acid in the small intestine.

Cecum

The first part of the large intestine, connected to the ileum of the small intestine.

Ascending Colon

The part of the large intestine that travels upward from the cecum.

Transverse Colon

The part of the large intestine that crosses the abdominal cavity from right to left.

Descending Colon

The part of the large intestine that travels downward on the left side of the abdomen.

Sigmoid Colon

The S-shaped last part of the large intestine leading into the rectum.

Segmentation

Rhythmic contractions of the small intestine that mix food with digestive juices and enhance absorption.

Hepatic Portal Vein

The blood vessel that carries nutrient-rich blood from the digestive organs to the liver.

Tunica Intima

Inner layer of an artery made of endothelial cells, providing a smooth surface for blood flow.

Tunica Media

Middle layer of an artery composed of smooth muscle and elastic fibers, allowing for contraction and expansion.

Tunica Externa (Adventitia)

Outer layer of an artery made of connective tissue, providing structural support and flexibility.

Elasticity in Arteries

Arteries, especially larger ones like the aorta, contain more elastic fibers, allowing them to stretch and recoil.

Function of Arteries

Arteries carry oxygenated blood away from the heart to various body tissues (except pulmonary arteries).

Tunica Intima (Veins)

Inner layer of a vein made of endothelial cells.

Tunica Media (Veins)

Middle layer of a vein, thinner than in arteries, with fewer smooth muscles and elastic fibers.

Tunica Externa (Adventitia) (Veins)

Outer layer of a vein, relatively thick, composed of connective tissue.

Valves in Veins

Veins, particularly in the limbs, contain valves to prevent backflow of blood and ensure unidirectional flow towards the heart.

Function of Veins

Veins carry deoxygenated blood back to the heart (except pulmonary veins).

Structure of Capillaries

Composed of a single layer of endothelial cells, facilitating easy exchange of materials.

Basement Membrane (Capillaries)

Lumen of Capillaries

Extremely narrow diameter, allowing red blood cells to pass through in single file.

Function of Capillaries

Facilitate the exchange of gases, nutrients, waste products, and hormones between blood and surrounding tissues.

Proximity of Capillaries to Cells

The extensive network ensures no cell is far from a blood supply, maximizing nutrient and waste exchange efficiency.

Atria

The two upper chambers of the heart (right atrium and left atrium) receive blood.

Ventricles

The two lower chambers of the heart (right ventricle and left ventricle) pump blood out of the heart.

Tricuspid Valve

Located between the right atrium and right ventricle.

Bicuspid (Mitral) Valve

Located between the left atrium and left ventricle.

Pulmonary Valve

Located between the right ventricle and the pulmonary artery.

Aortic Valve

Located between the left ventricle and the aorta.

Vena Cava

Superior and inferior vena cava bring deoxygenated blood from the body to the right atrium.

Pulmonary Arteries

Carry deoxygenated blood from the right ventricle to the lungs.

Pulmonary Veins

Bring oxygenated blood from the lungs to the left atrium.

Aorta

Carries oxygenated blood from the left ventricle to the body.

Atrial Systole

Atria contract, pushing blood into the ventricles through the open AV valves.

Diastole

Both atria and ventricles are relaxed, semilunar valves close, and AV valves open, allowing passive blood flow into ventricles.

Ventricular Systole

Ventricles contract, AV valves close, and semilunar valves open to allow blood to be ejected into arteries.

Isovolumetric Contraction

Ventricles begin to contract with all valves closed, increasing pressure without changing volume.

Ventricular Ejection

Increased ventricular pressure opens semilunar valves, and blood is ejected into the pulmonary artery and aorta.

Innate Immunity

The body's first line of defense against pathogens, involving non-specific mechanisms present from birth, such as physical barriers (skin, mucous membranes), chemical barriers (enzymes, stomach acid), and cellular defenses (phagocytes, natural killer cells).

Phagocytes

Immune cells that engulf and digest pathogens and debris. Examples include neutrophils and macrophages.

Natural Killer (NK) Cells

A type of lymphocyte that can kill virus-infected cells and tumor cells by inducing apoptosis.

Inflammatory Response

A defense mechanism triggered by tissue damage or infection, characterized by redness, heat, swelling, and pain to isolate and eliminate pathogens and promote healing.

Complement System

A group of blood proteins that enhance the immune response by promoting phagocytosis, inflammation, and cell lysis.

Adaptive Immunity

The body's second line of defense, providing specific responses to pathogens and involving the development of memory cells for long-term immunity.

B Cells

Lymphocytes that produce antibodies to neutralize pathogens or mark them for destruction.

Plasma Cells

Differentiated B cells that produce large amounts of antibodies.

Memory B Cells

Long-lived B cells that provide a faster and stronger response upon re-exposure to the same pathogen.

T Cells

Lymphocytes involved in cell-mediated immunity. Types include helper T cells, cytotoxic T cells, and regulatory T cells.

Helper T Cells (CD4⁺ T Cells)

T cells that activate and regulate other immune cells, including B cells and cytotoxic T cells, and produce cytokines to enhance the immune response.

Cytotoxic T Cells (CD8⁺ T Cells)

T cells that destroy infected or cancerous cells by recognizing specific antigens presented by these cells.

Regulatory T Cells

T cells that suppress immune responses to maintain homeostasis and prevent autoimmunity.

Major Histocompatibility Complex (MHC)

Molecules on cell surfaces that present antigens to T cells. MHC Class I molecules present endogenous antigens to cytotoxic T cells, while MHC Class II molecules present exogenous antigens to helper T cells.

Vaccines

Biological preparations that stimulate the immune system to recognize and combat specific pathogens by mimicking natural infections, leading to the development of memory cells for long-term immunity.

Antibody

Y-shaped protein produced by B cells that binds specifically to an antigen to neutralize it or mark it for destruction.

Lymphatic System

A network of tissues and organs, including lymph nodes, lymph vessels, and the spleen, that helps rid the body of toxins, waste, and other unwanted materials and facilitates immune responses.

Cytokines

Small proteins released by cells, especially immune cells, that act as signaling molecules to regulate immunity, inflammation, and hematopoiesis.

Chemokines

A type of cytokine that induces chemotaxis in nearby cells, directing them to the sites of infection or inflammation.

Antigen-Presenting Cells (APCs)

Immune cells, such as dendritic cells, macrophages, and B cells, that capture and present antigens to T cells, initiating the adaptive immune response.

Dendritic Cells

Specialized antigen-presenting cells that process antigen material and present it to T cells, acting as messengers between the innate and adaptive immune systems.

Macrophages

Large phagocytic cells derived from monocytes that engulf and digest pathogens, dead cells, and debris, and also function as antigen-presenting cells.

Neutrophils

The most abundant type of white blood cells that play a key role in the innate immune response by ingesting and destroying bacteria and fungi.

Pathogen

Any microorganism that can cause disease, such as bacteria, viruses, fungi, and parasites.

PAMPs (Pathogen-Associated Molecular Patterns)

Molecules associated with groups of pathogens that are recognized by cells of the innate immune system.

PRRs (Pattern Recognition Receptors)

Receptors on immune cells that recognize PAMPs and initiate an immune response.

Autoimmunity

An immune response against the body's own cells and tissues, leading to autoimmune diseases.

Immunodeficiency

A state in which the immune system's ability to fight infectious disease and cancer is compromised or entirely absent.

Herd Immunity

When a large portion of a community becomes immune to a disease, either through vaccination or previous infections, reducing the spread of the disease to individuals who are not immune.

Nose

The external part of the respiratory system; filters, warms, and moistens incoming air.

Nasal Cavity

The internal part of the nose lined with mucous membranes and hair; traps dust and pathogens.

Pharynx

A muscular tube that serves as a pathway for air and food; divided into nasopharynx, oropharynx, and laryngopharynx.

Nasopharynx

The upper part of the pharynx, connecting with the nasal cavity.

Oropharynx

The middle part of the pharynx, behind the mouth.

Larynx

Also known as the voice box; routes air and food into proper channels and contains vocal cords.

Laryngopharynx

The lower part of the pharynx, leading to the larynx and esophagus.

Thyroid Cartilage

A large cartilage of the larynx, commonly known as the Adam's apple.

Epiglottis

A flap of cartilage that covers the trachea during swallowing to prevent food from entering the airway.

Trachea

Also known as the windpipe; a tube supported by C-shaped cartilaginous rings, providing a clear airway to the lungs.

Primary Bronchi

The first branches of the trachea, leading into each lung.