Exam III Study Guide: Digestive, Metabolic, Urinary, and Reproductive Systems

Digestive System

Overview and Major Functions

The digestive system is responsible for the breakdown of food, absorption of nutrients, and elimination of waste. It consists of various organs, each with specialized functions.

• Major Organs: Mouth, esophagus, stomach, small intestine, large intestine, liver, pancreas, gallbladder.

• Functions: Ingestion, mechanical and chemical digestion, absorption, and excretion.

• Example: The stomach uses hydrochloric acid and enzymes to break down proteins.

Digestive Processes and Regulation

• Phases of Digestion: Cephalic, gastric, and intestinal phases regulate digestive activity.

• Neural and Hormonal Control: The enteric nervous system and hormones (e.g., gastrin, secretin) coordinate digestive processes.

• Additional info: The cephalic phase is triggered by sight, smell, or thought of food, stimulating gastric secretions.

Digestive Enzymes and Secretions

• Enzymes: Amylase (carbohydrates), pepsin (proteins), lipase (fats).

• Accessory Organs: Liver produces bile for fat emulsification; pancreas secretes digestive enzymes.

Metabolism and Energetics

Metabolic Pathways

Metabolism encompasses all chemical reactions in the body, including catabolic and anabolic pathways.

• Glycolysis: Breakdown of glucose to pyruvate, producing ATP.

• Krebs Cycle (Citric Acid Cycle): Oxidizes acetyl-CoA to CO2, generating NADH and FADH2.

• Electron Transport Chain: Uses NADH and FADH2 to produce ATP via oxidative phosphorylation.

• ATP Yield: Glycolysis: $2$ATP Krebs Cycle: $2$ ATP Electron Transport Chain: $32$ ATP (approximate total per glucose molecule)

• Additional info: Lipid and protein metabolism also contribute to energy production.

Energy Storage and Use

• Glycogenesis: Formation of glycogen from glucose.

• Gluconeogenesis: Synthesis of glucose from non-carbohydrate sources.

• Lipogenesis: Formation of lipids from acetyl-CoA.

• Example: During fasting, gluconeogenesis maintains blood glucose levels.

Urinary System

Structure and Function

The urinary system removes waste products from the blood and regulates water, electrolyte, and acid-base balance.

• Major Organs: Kidneys, ureters, bladder, urethra.

• Functions: Filtration, reabsorption, secretion, and excretion.

• Example: Kidneys filter blood to produce urine, which is stored in the bladder.

Nephron Structure and Function

• Nephron: Functional unit of the kidney, consisting of the renal corpuscle and renal tubule.

• Filtration: Occurs in the glomerulus; reabsorption and secretion occur in the tubules.

• Hormonal Regulation: Antidiuretic hormone (ADH) increases water reabsorption; aldosterone regulates sodium reabsorption.

Regulation of Glomerular Filtration Rate (GFR)

• Autoregulation: Maintains stable GFR despite changes in blood pressure.

• Hormonal Control: Renin-angiotensin-aldosterone system (RAAS) increases GFR; atrial natriuretic peptide (ANP) decreases GFR.

• Nervous Control: Sympathetic stimulation can decrease GFR during stress.

• Additional info: Tubuloglomerular feedback adjusts GFR based on sodium concentration in the distal tubule.

Reproductive System

Structure and Function

The reproductive system enables the production of offspring and the continuation of genetic material.

• Male Organs: Testes, epididymis, vas deferens, prostate, penis.

• Female Organs: Ovaries, fallopian tubes, uterus, vagina.

• Functions: Gametogenesis (sperm and egg production), hormone secretion, fertilization, and support of fetal development.

Hormonal Regulation

• Male: Testosterone regulates spermatogenesis and secondary sex characteristics.

• Female: Estrogen and progesterone regulate the menstrual cycle and pregnancy.

• Menstrual Cycle: Follicular phase: Estrogen promotes follicle development. Luteal phase: Progesterone prepares the endometrium for implantation.

• Additional info: The hypothalamic-pituitary-gonadal axis controls reproductive hormone secretion.

Fertilization and Development

• Fertilization: Fusion of sperm and egg to form a zygote.

• Development: Embryonic and fetal development occur in the uterus.

• Example: Human gestation lasts approximately 40 weeks.

Summary Table: Major Organ Systems and Functions

System	Main Organs	Primary Functions
Digestive	Mouth, stomach, intestines, liver, pancreas	Digestion, absorption, excretion
Urinary	Kidneys, ureters, bladder, urethra	Filtration, waste removal, water balance
Reproductive	Testes, ovaries, uterus, penis, vagina	Gamete production, hormone secretion, reproduction
Metabolic	Cellular organelles (mitochondria, cytoplasm)	Energy production, biosynthesis