Exam 4 Study Guide: Digestive System, Nutrition & Metabolism, Reproductive System, and Lymphatic/Immune System

Digestive System and Nutrition and Metabolism

Overview of the Digestive System

The digestive system is responsible for the breakdown of food, absorption of nutrients, and elimination of waste. It consists of the gastrointestinal (GI) tract and accessory organs.

• GI Tract: Includes mouth, pharynx, esophagus, stomach, small intestine, and large intestine.

• Accessory Organs: Salivary glands, liver, gallbladder, pancreas.

• Main Functions: Ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation.

Digestive System Structure and Function

• Histological Layers: Mucosa, submucosa, muscularis externa, serosa.

• Motility: Peristalsis and segmentation move and mix food.

• Secretions: Enzymes, acids, and hormones regulate digestion.

Accessory Organs and Their Roles

• Liver: Produces bile for fat emulsification; processes nutrients.

• Gallbladder: Stores and concentrates bile.

• Pancreas: Secretes digestive enzymes and bicarbonate.

Digestive Processes and Enzymes

• Carbohydrate Digestion: Begins in mouth (salivary amylase), continues in small intestine.

• Protein Digestion: Begins in stomach (pepsin), completed in small intestine (trypsin, chymotrypsin).

• Lipid Digestion: Begins in small intestine (bile, pancreatic lipase).

• Nucleic Acid Digestion: Pancreatic nucleases in small intestine.

Absorption and Transport

• Carbohydrates and Proteins: Absorbed as monosaccharides and amino acids into blood.

• Lipids: Absorbed as fatty acids and monoglycerides into lymph via chylomicrons.

Metabolism and Energy Balance

• Catabolism: Breakdown of molecules to release energy.

• Anabolism: Synthesis of complex molecules from simpler ones.

• ATP Production: Cellular respiration converts glucose to ATP.

Equation for Cellular Respiration:

$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + ATP$

Hormonal Regulation

• Gastrin: Stimulates gastric acid secretion.

• Secretin: Stimulates bicarbonate release from pancreas.

• Cholecystokinin (CCK): Stimulates bile and pancreatic enzyme release.

Nutrition and Dietary Considerations

• Macronutrients: Carbohydrates, proteins, fats.

• Micronutrients: Vitamins and minerals.

• Essential Nutrients: Must be obtained from diet.

Disorders and Clinical Applications

• Malabsorption: Impaired nutrient absorption (e.g., celiac disease).

• Enzyme Deficiencies: Lactase deficiency leads to lactose intolerance.

Reproductive System, Development, and Pregnancy

Male and Female Reproductive Anatomy

• Male: Testes, epididymis, vas deferens, seminal vesicles, prostate, penis.

• Female: Ovaries, uterine tubes, uterus, vagina, vulva.

Gametogenesis

• Spermatogenesis: Formation of sperm in seminiferous tubules.

• Oogenesis: Formation of ova in ovarian follicles.

Hormonal Regulation of Reproduction

• FSH and LH: Stimulate gamete production and hormone secretion.

• Estrogen and Progesterone: Regulate menstrual cycle and pregnancy.

• Testosterone: Regulates male secondary sex characteristics and spermatogenesis.

Menstrual and Ovarian Cycles

• Phases: Follicular, ovulation, luteal.

• Hormonal Influence: Estrogen peaks before ovulation; progesterone peaks after.

Fertilization and Embryonic Development

• Fertilization: Fusion of sperm and egg in uterine tube.

• Embryonic Membranes: Amnion, chorion, yolk sac.

• Placenta: Site of nutrient and gas exchange between mother and fetus.

Pregnancy and Birth

• Gestation: Divided into trimesters; fetal development occurs in uterus.

• Labor: Series of uterine contractions leading to birth.

• Lactation: Milk production by mammary glands.

Lymphatic System and Immune System

Lymphatic System Structure and Function

• Lymphatic Vessels: Transport lymph fluid from tissues to bloodstream.

• Lymphatic Organs: Lymph nodes, spleen, thymus, tonsils.

• Lymphatic Capillaries: Collect excess interstitial fluid.

Immune System Overview

• Innate Immunity: Non-specific defenses (skin, mucous membranes, phagocytes).

• Adaptive Immunity: Specific defenses (B cells, T cells, antibodies).

Cells and Molecules of Immunity

• B Lymphocytes: Produce antibodies; responsible for humoral immunity.

• T Lymphocytes: Cell-mediated immunity; cytotoxic and helper functions.

• Antibodies: Proteins that bind antigens and neutralize pathogens.

Immune Responses

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

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

• Active Immunity: Acquired through infection or vaccination.

• Passive Immunity: Acquired through transfer of antibodies (e.g., maternal antibodies).

Antigen Processing and Presentation

• Major Histocompatibility Complex (MHC): Presents antigens to T cells.

• Antigen-Presenting Cells (APCs): Dendritic cells, macrophages, B cells.

Disorders and Clinical Applications

• Autoimmunity: Immune system attacks self tissues (e.g., rheumatoid arthritis).

• Immunodeficiency: Impaired immune response (e.g., HIV/AIDS).

Summary Table: Comparison of Innate and Adaptive Immunity

Feature	Innate Immunity	Adaptive Immunity
Specificity	Non-specific	Specific to antigens
Memory	None	Memory cells present
Response Time	Immediate	Delayed (days)
Main Components	Barriers, phagocytes, inflammation	B cells, T cells, antibodies

Example: Vaccination induces adaptive immunity by stimulating antibody production against specific pathogens.