WP 5.2 Excretion PPT student (1)

Page 1: Practical and Laminate Codes

Important Notes

  • Practical Codes

    • 5.2.1 Excretion

    • 5.2.2 Structure of the Liver

    • 5.2.3 Liver Function

    • 5.2.4 Kidney Structure

    • 5.2.5/5.2.6 Function of the Kidney

    • 5.2.7 Osmoregulation

    • 5.2.8 Kidney Failure

Page 2: Learning Objectives for Excretion

5.2.1 Excretion

  • Define the term excretion.

  • Explain the importance of removing metabolic wastes such as carbon dioxide and nitrogenous waste from the body.

Page 3: Definition of Excretion

Excretion

  • Excretion is the removal of unwanted products of metabolism.

    • Main products include:

      • Carbon dioxide

      • Urea

      • Bile pigments

  • Further details on urea production will be discussed in relation to the liver.

  • Questions to consider:

    • Where does urea come from?

    • Can you draw the basic structure of an amino acid?

Page 4: Carbon Dioxide

Carbon Dioxide Production

  • Produced in every living cell during aerobic respiration.

  • Transported in the bloodstream and excreted from the lungs.

Page 5: Transport of Carbon Dioxide

Carbon Dioxide Transport

  • CO2 is carried in three ways:

    • 5% in solution in plasma as CO2

    • 10% combined with amino groups in hemoglobin (forming carbaminohemoglobin)

    • 85% as hydrogen carbonate ions (HCO3-)

Page 6: Formation of Hydrogen Carbonate

Carbon Dioxide Transport

  • CO2 is transported in the blood as hydrogen carbonate ions.

  • The enzyme carbonic anhydrase catalyzes the reaction:

    • CO2 + H2O ⇌ H2CO3

Page 7: Dissociation of Carbonic Acid

Transport Mechanism

  • Carbonic acid dissociates as follows:

    • H2CO3 ⇌ H+ + HCO3-

  • H+ ions associate with hemoglobin acting as a buffer, forming hemoglobinic acid (HHb).

Page 8: Chloride Shift

Mechanism of Balance

  • Build-up of HCO3- ions causes them to diffuse out of red blood cells (RBC).

  • Positively charged Cl- ions diffuse into RBC from plasma to balance electrical charge.

Page 9: Formation of HCO3-

Process of Formation

  1. CO2 combines with water to form carbonic acid (H2CO3), catalyzed by carbonic anhydrase.

  2. Carbonic acid dissociates to release H+ ions and HCO3-.

  3. HCO3- ions diffuse out of the RBC into plasma, while Cl- ions move into the cell (chloride shift).

  4. H+ ions create acidity, leading to hemoglobin acting as a buffer.

Page 10: Consequences of CO2 Buildup

Toxicity of Carbon Dioxide

  • If CO2 is not excreted:

    • It is toxic.

    • Hydrogen carbonate ions can reduce oxygen transport efficiency.

    • Forms carbaminohemoglobin which has lower oxygen affinity.

    • Can lead to respiratory acidosis:

      • Symptoms: low blood pH, headache, drowsiness, restlessness, tremor, confusion.

Page 11: Excretion Questions

Questions for Review

  1. List the excretory products found in sweat.

  2. What effects could the build-up of excess salts have in the blood?

  3. Explain how metabolic waste products affect enzyme action.

  4. Why is the majority of waste in feces not considered excretion?

  5. Why can fish excrete nitrogenous waste as ammonia, while mammals convert it to urea?

Page 12: Structure of the Liver Objectives

5.2.2 Structure of the Liver

  • Describe, with diagrams and photographs, the histology and gross structure of the liver.

Page 13: Anatomy of the Liver

Associated Organs

  • Structures include:

    • Hepatic artery

    • Liver

    • Aorta

    • Vena cava

    • Hepatic vein

    • Diaphragm

    • Gallbladder

    • Bile duct

    • Hepatic portal vein

    • Pancreas

    • Small intestine

Page 14: Histology of the Liver

Location and Blood Supply

  • The liver is located below the diaphragm, right of center.

  • Supplied by:

    • Hepatic artery: carries oxygenated blood from the aorta.

    • Hepatic portal vein: delivers blood from the digestive tract.

Page 15: Liver Lobes and Lobules

Lobular Structure

  • The liver has two principal lobes, which are subdivided into approximately 100,000 lobules.

Page 16: Components of the Lobule

Liver Structure

  • Structures within a lobule:

    • Hepatic cords

    • Central vein

    • Bile canaliculi

    • Hepatic sinusoids (structural and functional units containing hepatocytes).

Page 17: Blood Flow in the Liver

Blood Circulation

  • Blood exits the liver via the hepatic vein to the vena cava.

  • Approximately 75% of blood delivered arrives via the hepatic portal vein at low pressure.

Page 18: Lobule Structure

Components

  • Each lobule is a six-sided structure composed of specialized epithelial cells (hepatocytes).

Page 19: Hepatocyte Characteristics

Features of Hepatocytes

  • Hepatocytes contain:

    • Numerous mitochondria due to high metabolic activity.

    • Large nuclei for active DNA transcription.

  • Capable of division and replication, facilitating liver regeneration.

  • Blood from hepatic artery and portal vein mixes in sinusoids, increasing oxygen available for hepatocytes.

Page 20: Kupffer Cells

Function of Kupffer Cells

  • Located within the sinusoids, Kupffer cells are fixed phagocytes.

  • Their role is to destroy worn-out blood cells, bacteria, and foreign particles from the digestive tract.

Page 21: Bile Production

Bile Canaliculi and Ducts

  • Hepatocytes secrete bile into bile canaliculi, transporting it to the bile ducts and gallbladder.

Page 22: Liver Lobule Appearance

Structural Overview

  • Diagrams show the appearance and blood supply of a liver lobule, highlighting:

    • Central vein

    • Sinusoids

    • Hepatic lobules and their connections.

Page 23: Micrograph of Liver Lobule

Histological Analysis

  • Light micrograph magnified at x1400 showing:

    • Hepatocytes

    • Sinusoid

    • Kupffer cells

    • Central vein with blood cells.

Page 24: Bile Duct Function

Bile Transport

  • Hepatocytes secrete bile into bile canaliculi, which carry it out of the lobule into the bile ducts and subsequently to the gallbladder.

Page 25: Questions on Liver Structure

Review Questions

  1. Identify blood vessels:

    • a) Carrying deoxygenated blood to the liver high in nutrients.

    • b) Carrying oxygenated blood from the heart to the liver.

    • c) Carrying blood away from the liver.

  2. Complete the sentences:

    • a) A liver lobule is made up of [...] surrounded by [...] called [...].

  3. Label relevant diagrams.

  4. What is the function of this organ?

Page 26: Liver Functions and Detoxification

Liver Detoxification Role

  • The liver breaks down drugs like paracetamol, detoxifying harmful substances.

  • Understanding liver structure is key to learning its functions, including detoxification and metabolism.