a and p lecture 20

Schedule and Quizzes

• Last week of classes has more lectures and quizzes.

• Initially planned for 11 quizzes with 2 drop marks; now only 9 quizzes will count.

• Quiz 12 results will be available shortly after completion for feedback before the exam.

• All quizzes remain open until Friday, leading up to exams from Wednesday to Friday.

Large Intestine Overview

• Focus on sections of the large intestine: reabsorption of water, absorption of gut microbiome metabolites (e.g., vitamins).

• Pre-existing nutrients are digested before reaching the large intestine; no new secretion or digestion occurs here.

• The descending colon and sigmoid colon primarily store fecal matter, enabling normal daily bowel movements.

Digestion of Nutrients

• Enzymes play crucial roles in the digestion of proteins, lipids (easier), and carbohydrates (more complex).

• Structural diversity of carbohydrates leads to a broader range of enzymes needed for effective breakdown.

• Brief mention of lactose intolerance variations across populations influenced by historical mutations.

Gas Production and Carbohydrates

• Starch comes from plants, serving as energy stores, while cellulose cannot be digested by humans but is essential for some animals with specialized gut microbiomes.

• Mechanisms of absorption of monosaccharides:

  • Active transport for glucose using sodium gradient.

  • Fructose absorbed via facilitated diffusion.

Vitamin and Ion Absorption

• Vitamins are absorbed directly; fat-soluble vitamins (A, D, E, K) diffuse across membranes, while vitamin B12 needs intrinsic factor for absorption.

• Mineral absorption involves mostly active transport, especially for iron, which binds to ferritin for storage in the body.

Water and Transport Mechanisms

• Approximately 9 liters of pancreatic juice are produced daily, with a significant portion recovering in the intestines.

• Overview of various transport mechanisms: passive transport, facilitated diffusion, and active transport mechanisms essential for nutrient absorption.

Kidney and Renal System Overview

• Functionality: toxin removal, storage of nitrogenous waste products, regulation of ion concentration, and water balance.

• Importance of kidney regulation in maintaining blood pressure and ensuring proper ion gradients for physiological processes.

Anatomy of the Kidney

• Presentation of kidney structure and functionality; nephrons are the functional units that produce urine.

• The outer renal cortex vs. inner renal medulla structure.

• Nephron Functionality

  • Each nephron produces primary urine, which undergoes modifications before reaching the bladder.

  • Statistically speaking, about 160 liters of primary urine are formed per day, with only 2 liters being excreted.

  • The filtration process involves blood pressure-driven ultrafiltration at the renal corpuscle applying various mechanisms for controlled release.

Integration of Structures and Functions

• Connection of kidneys to circulatory systems via renal artery/vein for blood filtration efficiency.

• Mechanisms allow for urine concentration variations based on hydration levels.