Digestive and Urinary Systems Overview

Functioning Systems

The presentation covers the functioning of systems in the body, specifically the digestive and urinary systems.
The lecturer's name is Prof. Dr. Eman Salah Abdel-Reheim.

Food Assimilation

Learning Objectives: Students will learn about the general function of the digestive system, mechanical and chemical digestion, simplest forms of nutrients, and absorption.
Functions of the Digestive System: The system breaks down food into molecules, absorbs them into the blood, and then carries them throughout the body. Wastes are eliminated from the body.
Digestion: The process by which the body breaks down food into small nutrient molecules.
Types of Digestion:
- Mechanical Digestion: Physically breaking down food into smaller pieces. Starts with chewing (mastication) by teeth.
- Chemical Digestion: Breaking down food into smaller building blocks using chemicals produced by the body. Begins in the mouth.
Mechanical Digestion Expressions:
- Mastication: Chewing and enzymatic breakdown by saliva.
- Deglutition: The act of swallowing; voluntary in the mouth and involuntary in the esophagus.
Mechanical Digestion Examples:
- Churning: In the stomach, forming chyme.
- Peristalsis: Contraction of circular muscle.
- Segmentation: Contraction of longitudinal muscle (backward and forward movement) until the colon.
Chemical Digestion - Digestive Juices:
- Saliva from parotid, sublingual, and submandibular glands.
- Gastric juice (pepsin and HCl).
- Pancreatic juice.
- Bile, produced by the liver, stored in the gall bladder, and secreted in small intestine, aiding lipid digestion.
- Intestinal juice, secreted by the mucosa of the small and large intestine.
Chemical Digestion (Enzymes):
- Mouth: Carbohydrates - salivary amylase.
- Stomach: Proteins - pepsin.
- Small intestine:
  - Lipids - trypsin, chymotrypsin, amylase, and lipase (from pancreas).
  - Maltase, sucrase, lactase, peptidases (from intestinal villi)

Absorption

After digestion, the simplest forms of food (glucose, amino acids, and fatty acids) are absorbed.
Absorption is the passage of these nutrients through the intestinal mucosa into the blood.
Amino acids and glucose are transported into the blood via secondary active transport.
Fatty acids enter the lymph via simple diffusion.

Metabolism

Catabolism: Breaking down complex materials (hydrolysis), releasing energy (cellular respiration).
Anabolism: Building complex materials; for cell maintenance, repair, growth, secretion, and nutrient reserves.
Metabolic Processes:
- Glucose - glycolysis, Kreb's cycle, electron transport chain, glycogenesis, gluconeogenesis
- Fatty Acids - beta-oxidation, Kreb's cycle, electron transport chain, lipogenesis
- Amino Acids - deamination, Kreb's cycle, electron transport chain, synthesis of nonessential amino acids.

Urinary System

Learning Objectives: Students will learn about the functions, anatomy, nephron structure, urine formation process (filtration, reabsorption, secretion), urine composition, factors affecting kidney function, and hemodialysis.
Functions of the Urinary System:
- Regulate blood composition: Maintaining homeostasis.
- Remove metabolic waste: Urea, creatinine, ammonium, uric acid.
- Maintain water-salt/electrolyte balance: Sodium, potassium, bicarbonate.
- Maintain acid-base balance: Maintain a blood pH of approximately 7.4.
Structure and Anatomy of the Urinary System: includes organs like kidneys, ureters, urinary bladder, urethra.
Kidney Anatomy: Protected by fat, muscle, and ribs, and consists of renal cortex, medulla, pelvis.
Nephron Structure: Structural and functional unit of the kidney, consisted of renal corpuscle (glomerular capsule and capillary network), and renal tubules (proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule (DCT)).
Urine Formation Steps:
- Filtration: Removal of water and small molecules from blood.
- Reabsorption: Return of water and essential molecules from filtrate to blood.
- Secretion: Addition of wastes and excess salts from body fluids to the filtrate (urine).
Glomerular Filtration Rate: The amount of filtrate produced by the kidneys each minute; approximately 125-130 ml.
Forces Affecting Filtration: Glomerular capillary hydrostatic pressure, blood osmotic pressure, and capsular hydrostatic pressure.
Reabsorption Processes:
- In PCT: Reabsorption of 70% sodium and water through osmosis & simple diffusion
- In Loop of Henle: Active transport, osmosis (for water) to concentrate/dilute urine.
- In DCT & CT: Hormone-regulated reabsorption of water (ADH) and sodium (aldosterone) is "facultative" as it depends on the body's needs.
Secretion and Excretion: Selective transport of molecules from blood to the renal tubule lumen. Removal of urine from tubular system to outside the body.
Urine Composition: Primarily water, with urea, uric acid, and electrolytes.
Factors Affecting Kidney Function: ADH, alcohol, aldosterone, caffeine, and blood pressure.
Kidney Diseases, Dialysis, and Transplantation: Overview of kidney diseases, medical treatments such as dialysis and transplantation.
Hemodialysis: A technique to filter blood when kidneys fail; wastes are removed via a dialysis machine (using a semipermeable membrane).