The Urinary System Chapter 24 Lecture Notes

1
The Urinary SystemChapter 24 Lecture Notes

• to accompany
• Anatomy and Physiology From Science to Life
• textbook by
• Gail Jenkins, Christopher Kemnitz, Gerard Tortora

2
Chapter Overview

• 24.1 Kidney Functions
• 24.2 Urinary Path
• 24.3 Nephron Structure
• 24.4 Nephron Function
• 24.5 Glomular Filtration
• 24.6 Tubular Reabsorption and Secretion
• 24.7 Hormonal Regulation
• 24.8 Antidiuretic Hormone
• 24.9 Urine Transport
• 24.10 Fluid and Acid-Base Balance

3
Essential Terms

• kidney
• produces urine to remove waste from the body by
  filtration of blood
• nephron
• structure within kidney that actually filters the
  blood and composed of several parts
• nitrogen waste
• produced by protein catabolism
• micturition
• process of releasing urine from the body

4
Introduction

• Urinary System
• Eliminates non-useful metabolic byproducts such
  as nitrogenous wastes
• Comprised of two kidneys, two, ureters, one
  urinary bladder and one urethra
• Returns most water and useful solutes are to
  bloodstream
• Urine results from filtration of blood plasma
• Kidneys help maintain homeostasis

5
Concept 24.1Kidney Functions
6
Kidney Functions

• Regulate various properties of the blood
• Ionic composition
• pH
• Volume
• Pressure
• Glucose level
• Produces hormones
• Excretes waste and foreign substances

7
Figure 24.1
8
Concept 24.2 Urinary Path
9

• Paired kidneys are retroperitoneal organs
• Renal hilum
• Area for entry and exit of nerves, blood and
  lymphatic vessels and ureter exit
• 3 layers of connective tissue
• Renal capsule deep
• Maintains shape and forms barrier
• Adipose capsule middle
• Cushions and supports
• Renal fascia superficial
• Anchors to abdominal wall

10
Figure 24.2a
11
Figure 24.2b
12
Internal Anatomy

• Renal cortex
• Renal Medulla
• Renal Pyramids
• Renal papilla
• Renal columns
• Renal lobe
• Nephrons functional unit of kidney, filters
  blood
• Papillary ducts
• Minor and major calyces
• Renal pelvis
• Renal sinus

13
Figure 24.3a
14
Figure 24.3b
15
Blood Supply

• Renal arteries
• Afferent vessels supply 20 - 25 of resting
  cardiac output
• Segmental arteries
• Interlobar arteries
• Arcuate arteries
• Interlobular arteries
• Afferent arteriole
• One per nephron and divides into glomerulus
• Glomerulus
• Network of glomerular capillaries to filter blood

16
(No Transcript)
17
Figure 24.4b
18
Blood Supply

• Glomerulus
• Glomerular capillaries form efferent arteriole
• Peritubular capillaries
• Vasa recta
• Interlobular veins
• Arcuate veins
• Interlobar veins
• Renal vein
• Efferent vessel carries blood to inferior vena
  cava

19
Concept 24.3 Nephron Structure
20
2 Parts of Nephron

• Renal corpuscle
• Filters blood plasma
• Glomerulus
• Glomerular (Bowmans) capsule
• Renal tubule
• Refines filtered fluid
• Proximal convoluted tubule (PCT)
• Loop of Henle (LOH)
• Distal convoluted tubule (DCT)

21
Figure 24.5a
22
Figure 24.5b
23
Nephron Structure

• Loop of Henle
• Descending limb of loop of Henle
• Ascending limb of loop of Henle
• Cortical nephrons 80-85 of nephrons
• Corpuscles in outer cortex with short loops of
  Henle
• Juxtamedullary nephrons 15-20
• Corpuscles deep in cortex with long loops of
  Henle
• Thin and thick ascending limb
• Distal convoluted tubule
• Collecting duct
• Papillary ducts

24
Nephron Structure Histology

• Glomerular Capsule
• Podocytes
• Capsular space
• Renal tubule and collecting duct
• Macula densa
• Juxtaglomerular (JG) cells
• Both comprise Juxtaglomerular (JGA) apparatus
• Regulate blood pressure within kidneys

25
Figure 24.6a
26
Figure 24.6b
27
Concept 24.4 Nephron Function
28
Functions of Nephron

• Glomerular filtration
• Tubular reabsorption
• Tubular secretion
• Removes substances from blood as waste

29
Figure 24.7
30
Concept 24.5 Glomerular Filtration
31
Filtration Membrane

• Leaky barrier formed by endothelial cells and
  podocytes
• 3 layers
• Glomerular endothelial cell
• Fenestrations
• Mesangial cells
• Basal lamina
• Pedicles form filtration slits

32
Figure 24.8a
33
Figure 24.8b
34
Filtration Process

• Use of pressure to force fluids and solutes
  through a membrane
• 3 reasons for large volume through renal
  corpuscles
• Large surface area of glomerular capillaries
• Mesangial cells
• Thin, porous filtration membrane
• High glomerular capillary blood pressure

35
Net Filtration Pressure (NFP)

• NFP GBHP CHP BCOP
• Glomerular blood hydrostatic pressure (GBHP)
• Promotes filtration
• Capsular hydrostatic pressure (CHP)
• Opposes filtration
• Blood colloid osmotic pressure (BCOP)
• Opposes filtration

36
Figure 24.9
37
Glomerular Filtration Rate (GFR)

• Mechanisms that affect filtration pressure
• Adjust blood flow
• Alter available glomerular capillary surface area
• GFR controlled by 3 mechanisms
• Renal autoregulation
• Negative feedback by macula densa
• Neural regulation
• Hormonal regulation

38
Figure 24.10
39
Renal Autoregulation

• Renal Autoregulation
• Myogenic mechanism
• Tubuloglomerular feedback
• Neural Regulation
• Sympathetic neurons release norepinephrine to
  vasoconstrict afferent arterioles
• Hormonal Regulation
• Angiotensin II reduces GFR
• Atrial natriuretic peptide (ANP) increases GFR

40
Table 24.1
41
Hormonal Regulation of Tubular Reabsorption and
Secretion

• Angiotensin II and Aldosterone
• Regulate electrolyte reabsorption and secretion
• Antidiuretic hormone (AH)
• Water reabsorption
• Atrial natriuretic peptide
• Inhibits electrolyte and water reabsorption

42
Renin-Angiotensin-Aldosterone System

• Blood pressure decrease results in renin release
  by JG cells
• Renin converts angiotensin into Angiotensin I
• Angiotensin I converted to active form
  Angionensin II which
• Decreases glomerular filtration rate
• Enhances reabsorption of NA, Cl-, and water
• Stimulates release of aldosterone to reabsorb
  more Na, Cl-, and water

43
Antidiuretic Hormone / Vasopressin

• Released by posterior pituitary
• Regulates facultative water reabsorption
• Principal cells
• Negative feedback mechanism
• ADH release stimulated by decreased
• Blood water concentration in blood
• Blood volume

44
Figure 24.17
45
Atrial Natriuretic Peptide

• Inhibits electrolyte and water reabsorption
• Released from heart in response to large increase
  in blood volume
• Suppresses secretion of aldosterone and ADH
• Results in increased urine output to decrease
  blood volume and blood pressure

46
Table 24.3