Immunology

Specific vs. Non-Specific Defenses

The immune system protects the body through two main types of defenses: non-specific (innate) and specific (adaptive) immunity.

• Non-Specific (Innate) Defenses: General mechanisms that defend against any pathogen. Includes physical barriers (skin, mucous membranes), phagocytic cells, natural killer cells, inflammation, and fever.

• Specific (Adaptive) Defenses: Target particular pathogens. Involves lymphocytes (B and T cells) and the production of antibodies.

• Example: Skin acts as a non-specific barrier, while antibodies produced against a specific virus are part of specific immunity.

Inflammation and Fever

Both are key components of the innate immune response.

• Inflammation: Localized tissue response to injury or infection, characterized by redness, heat, swelling, and pain. It helps isolate pathogens and recruits immune cells.

• Fever: Systemic increase in body temperature, often triggered by pyrogens. Fever can inhibit pathogen growth and enhance immune activity.

Immune System Cell Types

• Neutrophils: Phagocytic cells that ingest and destroy pathogens.

• Macrophages: Large phagocytes that also present antigens to T cells.

• Lymphocytes: Include B cells (produce antibodies) and T cells (mediate cellular immunity).

• Natural Killer (NK) Cells: Destroy virus-infected and cancerous cells.

B and T Lymphocytes

• B Lymphocytes (B cells): Mature in bone marrow, responsible for humoral immunity by producing antibodies.

• T Lymphocytes (T cells): Mature in the thymus, responsible for cell-mediated immunity. Types include helper T cells (CD4+) and cytotoxic T cells (CD8+).

• Production: Both originate from hematopoietic stem cells in bone marrow.

Key Terms

• Antigen: Any substance that can provoke an immune response.

• Antibody: Protein produced by B cells that binds specifically to an antigen.

• Immunocompetence: The ability of the immune system to recognize and respond to antigens.

Cell-Mediated vs. Humoral Immunity

• Cell-Mediated Immunity: Involves T cells attacking infected or abnormal cells directly.

• Humoral Immunity: Involves B cells and the production of antibodies that neutralize pathogens in body fluids.

Active vs. Passive Immunity

• Active Immunity: Results from direct exposure to an antigen (infection or vaccination); long-lasting due to memory cell formation.

• Passive Immunity: Transfer of antibodies from another source (e.g., maternal antibodies, antibody therapy); temporary protection.

Vaccines and Antigenic Stability

• Vaccines: Stimulate active immunity by exposing the immune system to harmless forms of antigens.

• Hepatitis B Vaccine: Uses recombinant technology; differs from traditional vaccines by using a viral protein produced in yeast.

• Antigenic Stability: Refers to how much a pathogen's antigens change over time. High variability (as in HIV) makes vaccine development difficult.

Primary and Secondary Immune Responses

• Primary Response: First exposure to an antigen; slower and less robust.

• Secondary Response: Subsequent exposures; faster and stronger due to memory cells.

Monoclonal Antibodies

• Definition: Identical antibodies produced by a single clone of B cells; used in diagnostics and therapy.

• Applications: Cancer treatment, autoimmune disease therapy, laboratory tests.

Immunodeficiencies vs. Autoimmune Diseases

• Immunodeficiencies: Conditions where the immune system is underactive (e.g., HIV/AIDS).

• Autoimmune Diseases: Immune system attacks the body's own tissues (e.g., lupus, type 1 diabetes).

HPV and Cancer; HPV Vaccine

• HPV: Human papillomavirus, associated with cervical and other cancers.

• HPV Vaccine: Prevents infection with cancer-causing HPV strains.

Digestive Physiology

One-Way Gut Advantage

• Definition: A digestive tract with separate mouth and anus allows for continuous, unidirectional processing of food.

• Advantage: Enables specialization of digestive regions and more efficient nutrient absorption.

Functions and Challenges of the Digestive System

• Functions: Ingestion, digestion, absorption, motility, secretion, and elimination.

• Challenges: Protecting against pathogens, digesting diverse foods, and absorbing nutrients efficiently.

Processes of Digestion

• Digestion: Breakdown of food into absorbable molecules.

• Absorption: Uptake of nutrients into blood or lymph.

• Motility: Movement of food through the GI tract via peristalsis and segmentation.

• Secretion: Release of digestive enzymes, acids, and mucus.

Organization and Anatomy of the Digestive System

• General Structure: Four tunic layers: mucosa, submucosa, muscularis externa, serosa.

• Microscopic Anatomy: Varies by region; e.g., villi in small intestine increase surface area for absorption.

Functions and Secretions of GI Tract Components

Zymogens and Stomach pH

• Zymogens: Inactive enzyme precursors; prevent self-digestion of tissues.

• Low pH in Stomach: Activates pepsinogen to pepsin, denatures proteins, and kills pathogens.

• Stomach Protection: Mucus and bicarbonate layer protect stomach lining from acid.

Accessory Organs

Digestive System Disorders

• Examples: Peptic ulcers, GERD, Crohn's disease, lactose intolerance.

Renal Physiology

Anatomy and Microanatomy of Kidney and Nephron

• Kidney: Bean-shaped organ; filters blood, forms urine.

• Nephron: Functional unit; consists of glomerulus, Bowman's capsule, proximal tubule, loop of Henle, distal tubule, and collecting duct.

Functions of the Kidney

• Regulates fluid and electrolyte balance

• Removes metabolic wastes

• Regulates blood pressure and pH

• Produces hormones (e.g., erythropoietin, renin)

Bladder Plasticity

• Definition: The ability of the bladder to stretch and accommodate varying volumes of urine without a significant increase in internal pressure.

UTIs and Gender Differences

• UTIs: More common in women due to shorter urethra and proximity to the anus.

Urine Formation Processes

• Filtration: Blood plasma filtered at glomerulus.

• Reabsorption: Movement of substances from filtrate back into blood.

• Secretion: Active transport of substances from blood into filtrate.

• Excretion: Removal of urine from the body.

Glomerulus Function and GFR Regulation

• Glomerulus: Capillary network where filtration occurs.

• GFR (Glomerular Filtration Rate): Rate at which filtrate is formed; regulated by blood pressure, afferent/efferent arteriole diameter, and hormones.

Reabsorption of Salt and Water

• Proximal Tubule: Reabsorbs most water, Na+, glucose, and amino acids.

• Loop of Henle: Descending limb permeable to water; ascending limb permeable to ions but not water.

• Distal Tubule and Collecting Duct: Regulated reabsorption of water and ions, influenced by hormones.

Countercurrent System

• Definition: Mechanism in the loop of Henle that creates a concentration gradient in the medulla, allowing for water reabsorption and concentrated urine.

Vasopressin Function

• Vasopressin (ADH): Increases water reabsorption in the collecting duct by inserting aquaporins into the membrane.

Renin-Angiotensin-Aldosterone System (RAAS)

• Function: Regulates blood pressure and fluid balance.

• Steps: Renin release → angiotensin II formation → aldosterone secretion → increased Na+ and water reabsorption.

Urine Osmolarity Regulation

• Variability: Controlled by ADH, medullary gradient, and water intake.

Reproductive Physiology

Advantage of Sexual Reproduction

• Biological Advantage: Increases genetic diversity, enhancing adaptability and survival.

Gender Determination in Humans

• Chromosomal Basis: XX = female, XY = male. The SRY gene on the Y chromosome initiates male development.

Testes Location

• Reason: Testes are outside the body cavity to maintain a temperature optimal for spermatogenesis (about 2-3°C below core body temperature).

Erection Reflex

• Mechanism: Parasympathetic stimulation causes vasodilation of penile arteries, leading to erection.

Testes and Ovaries: Exocrine and Endocrine Secretions

Fluids Secreted with Sperm

• Seminal Vesicles: Fructose-rich fluid for energy.

• Prostate Gland: Alkaline fluid to neutralize vaginal acidity.

• Bulbourethral Glands: Mucus for lubrication.

Male vs. Female Reproductive Hormones

• Male: Testosterone (primary), FSH, LH.

• Female: Estrogen, progesterone, FSH, LH.

Spermatogenesis vs. Oogenesis

• Spermatogenesis: Continuous production of sperm from puberty onward; four sperm per precursor cell.

• Oogenesis: Cyclical production of eggs; one ovum and polar bodies per precursor cell; begins before birth, completes at ovulation/fertilization.

Female Reproductive Tract Discontinuity

• Significance: The ovary is not directly connected to the fallopian tube, increasing risk of ectopic pregnancy.

Female Menstrual Cycle

• Hormones: FSH, LH, estrogen, progesterone.

• Ovary Stages: Follicular phase, ovulation, luteal phase.

• Uterus Stages: Menstrual, proliferative, secretory phases.

Contraceptive Methods

• Barrier Methods: Prevent sperm from reaching egg (e.g., condoms).

• Hormonal Methods: Suppress ovulation (e.g., birth control pills).

• IUDs: Prevent implantation or fertilization.

• Effectiveness: Varies; hormonal and IUDs are among the most effective.

Clinical Conditions

• Examples: Polycystic ovary syndrome (PCOS), erectile dysfunction, infertility, endometriosis.