Lab_10__Renal

Overview of the Urinary System

• Authors and Copyright: P. Pearson, © 2019, 2016 Pearson Education, Inc. All Rights Reserved

Structures of the Urinary System

Anterior View

• Diaphragm

• Adrenal Gland

• Aorta

• Kidney

• Ureter

• Urinary Bladder

• Urethra

Posterior View

• Inferior Vena Cava

• Vertebral Column

• 11th and 12th ribs

Kidney Function and Homeostasis

• Function:

  • Kidneys regulate homeostatic processes:

    • Filtration of Blood: Removes metabolic wastes, excreted as urine.

    • Fluid and Electrolyte Balance: Regulates osmolarity by conserving or eliminating water and electrolytes.

    • Acid-Base Balance: Maintains blood pH by regulating hydrogen ions and bicarbonate ions.

Anatomy of the Kidneys

External Anatomy

• Size: Approximate size of a bar of soap once connective tissue is removed.

• Hilum: Opening on the medial surface of the kidney where:

  • Renal artery and vein, nerves, and ureters enter and exit.

Internal Anatomy

• Layers:

  • Renal Cortex: Outermost layer.

  • Renal Medulla: Middle layer containing urine-forming structures.

  • Renal Pelvis: Innermost layer that drains the formed urine.

• Nephrons: Over one million per kidney, consisting of:

  • Renal Corpuscle: Glomerulus (ball-shaped capillaries) and Bowman's capsule.

  • Renal Tubule: Long tubule; most in cortex with some extending into medulla.

Urine Formation Process

Structure Breakdown

• Renal Pyramids: Cone-shaped structures in the renal medulla.

  • Minor and major calyces collect and drain urine into the renal pelvis; smooth muscle contractions help propel urine towards the ureter.

Blood Supply

• Kidney's Unique Capillary System:

  • Afferent Arterioles: Feed the glomerulus.

  • Efferent Arterioles: Drain the glomerulus into peritubular capillaries.

Nephron Functionality

Nephron Structure

• Renal Corpuscle: Filters blood effectively.

  • Glomerulus: Permeable and “leaky” capillaries for filtration.

  • Filtration Slits: Formed by podocytes in Bowman's capsule.

• Tubules:

  • Proximal Tubule: Longest segment for reabsorption.

  • Nephron Loop (Loop of Henle): Contains descending and ascending limbs.

  • Distal Tubule: Last segment before collection into ducts.

Reabsorption and Secretion Mechanisms

• Glomerular Filtration: Filters blood selectively based on particle size.

• Tubular Reabsorption: Reclaims water, glucose, electrolytes back into circulation.

• Tubular Secretion: Adds substances from blood into filtrate for excretion.

Renal Physiology Overview

Factors Affecting Glomerular Filtration Rate (GFR)

• Systemic Blood Pressure: Lower pressure leads to lower GFR.

• Vasodilatory Responses: Enhance GFR by increasing renal blood flow.

Hormonal Control

• ADH: Increases water reabsorption, reducing urine output.

• Aldosterone: Increases sodium and water retention.

Urine Production and Concentration

Mechanisms for Urine Concentration

• Countercurrent Mechanism: In the nephron loop, facilitates water and sodium reabsorption leading to concentrated urine.

• ADH Role: Presence enhances water reabsorption in collecting ducts.

Urine Composition and Analysis

Urinalysis

• Analyzes urine for diagnostics, focusing on:

  • Color: Influenced by hydration levels (urochrome).

  • Clarity: Cloudy urine can indicate infection or excess protein.

Histology of the Urinary Tract

Ureter Structure

• Layers:

  • Adventitia: Most superficial layer for support.

  • Muscularis: Smooth muscle layer for peristalsis.

  • Mucosa: Transitional epithelium for expansion.

Urinary Bladder Structure

• Distensible Organ: Empties to collapse and expands when full.

• Detrusor Muscle: Contracts to aid in urine expulsion.

Anatomy of the Urethra

• Differences in Male and Female Urethra:

  • Female: Short, only for urine transport.

  • Male: Longer, with three regions serving different functions.

Micturition Process

• Definition: The act of urination.

• Micturition Reflex: Triggered by bladder stretch receptors leading to detrusor contraction and sphincter relaxation.

Vocabulary Terms

• Albumin: Soluble protein, significant in urine analysis.

• Casts: Tube-shaped particles indicating kidney issues.

• Hemoglobin: Oxygen transport protein, relevant in urinalysis for blood presence.

• Ketones: Byproducts of fat metabolism significant in diabetes.

• Urinalysis: Comprehensive urine testing for health diagnostics.