View
227
Download
2
Category
Preview:
Citation preview
Chapter 15The Urinary System
Functions of the Urinary SystemFunctions of the Urinary System1. Elimination of waste
Nitrogenous wastes
Toxins
Drugs
2. Regulates homeostasis
Water balance
Electrolytes
Acid-base balance in the blood
Blood pressure
RBC blood cell production
Activation of vit. D
Organs of the Urinary systemOrgans of the Urinary system
Kidneys
Ureters
Urinary bladder
Urethra
Location of the KidneysLocation of the Kidneys
Against dorsal wall
T12 to L3
Right lower than left
Attached to ureters, renal blood vessels, & nerves at renal hilus
Atop kidney is adrenal gland
Coverings of the KidneysCoverings of the Kidneys1. Renal capsule
Surrounds kidney
2. Adipose capsule Surrounds kidney
protection
keeps kidney in location
Regions of the KidneyRegions of the Kidney
Renal cortex – outer region
Renal medulla – inside the cortex
Renal pelvis – inner collecting tube
Kidney StructuresKidney Structures Medullary pyramids
– triangular regions of tissue in medulla
Renal columns – extensions of cortex-like material inward
Calyces – cup-shaped structures that funnel urine towards renal pelvis
Blood Flow in the KidneysBlood Flow in the Kidneys
NephronsNephrons Structural and
functional units of the kidneys
Forms urine
Main structures
a. Glomerulus
b. Renal tubule
GlomerulusGlomerulus
Capillaries covered with podocytes from the renal tubule
Glomerulus sits within a glomerular capsule (1st part of the renal tubule)
Specialized capillary bed
Arterioles on both sides (maintains high pressure)
- Large afferent arteriole
- Narrow efferent arteriole
Renal TubuleRenal Tubule Glomerular
(Bowman’s) capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Types of NephronsTypes of Nephrons1. Cortical
entirely in cortex
most nephrons
2. Juxtamedullary at boundary of
cortex & medulla
Urine FormationUrine Formation Filtration
Reabsorption
Secretion
Peritubular CapillariesPeritubular Capillaries Arise from efferent arteriole
Normal, low pressure capillaries
Attached to venule
Cling to renal tubule
Reabsorb substances from collecting tubes
FiltrationFiltration Nonselective passive process
Water and solutes smaller than proteins are forced through capillary walls
Blood cells cannot pass out to the capillaries
Filtrate is collected in the glomerular capsule and leaves via the renal tubule
ReabsorptionReabsorption Peritubular capillaries reabsorb
- Some water, Glucose, Amino acids, Ions
Some passive, most active
Most reabsorption occurs in proximal tubule
Nitrogenous waste products
- Urea
- Uric acid
- Creatinine
Excess water
Not ReabsorbedNot Reabsorbed
Secretion – Reabsorption in ReverseSecretion – Reabsorption in Reverse Materials move from peritubular capillaries into
renal tubules
- H+ & K+
- Creatinine
Materials left in renal tubule move to ureter
Formation of UrineFormation of Urine
Figure 15.5
Characteristics of UrineCharacteristics of Urine
Yellow due to pigment urochrome (from break-down of hemoglobin) & solutes
Sterile
Slightly aromatic
Normal pH of ~ 6
Specific gravity of 1.001 to 1.035
UretersUreters
Slender tubes from kidney to bladder
- Continuous with renal pelvis
- Enter the posterior aspect of the bladder
Runs behind the peritoneum
Peristalsis aids gravity in urine transport
Urinary BladderUrinary Bladder Smooth, collapsible,
muscular sac
Temporarily stores urine
Trigone – 3 openings
- Two from ureters
- One to urethrea
Urinary Bladder WallUrinary Bladder Wall
Detrusor muscle – pushes down
3 layers of smooth muscle
Walls - thick & folded in empty bladder
Transitional epithelium - expands without increasing internal pressure
UrethraUrethra Thin-walled tube
Carries urine from bladder by peristalsis
Release controlled by 2 sphincters
- Internal urethral sphincter (involuntary)
- External urethral sphincter (voluntary)
Urethra Gender DifferencesUrethra Gender Differences
Length
- Females – 3–4 cm (1 inch)
- Males – 20 cm (8 inches)
Location
- Females – along wall of the vagina
- Males – through the prostate and penis
Function
- Females – only urine
- Males –urine and sperm
Micturition (Voiding)Micturition (Voiding)
Both sphincters must open
- internal relaxes after bladder stretches
- Activation - impulse to spinal cord and back via pelvic splanchnic nerves
- external voluntarily relaxes
Maintaining Water BalanceMaintaining Water Balance
Normal amount of water in humans
- Adult females – 50%
- Adult males – 60%
- Babies – 75%
- Old age – 45%
Water is necessary for many functions and levels must be maintained
Water intake = water output
Sources for water intake
- foods and fluids
- metabolic processes
Sources for water output- Vaporization from lungs
- perspiration
- feces
- Urine
Distribution of Body FluidDistribution of Body Fluid
Intracellular fluid (inside cells)
Extracellular fluid (outside cells)
- Interstitial fluid
- Blood plasma
Figure 15.7
Link Between Water and SaltLink Between Water and Salt
Changes in electrolyte balance causes water to move from one compartment to another
- Alters blood volume & blood pressure
- Can impair the activity of cells
Regulation of ReabsorptionRegulation of Reabsorption
Hormones
- Antidiuretic hormone (ADH) prevents excessive water loss in urine
- Aldosterone regulates sodium
- Triggered by the renin-angiotensin mechanism
Monitored by kidneys and hypothalamus
Maintaining Blood pHMaintaining Blood pH Normal Blood pH
- Alkalosis – pH above 7.45
- Acidosis – pH below 7.35
Most ions are metabolic byproducts
Most pH balance is maintained by kidneys
Other acid-base controlling systems
- Blood buffers
- Respiration
Blood BuffersBlood Buffers Molecules to prevent dramatic changes in [H+]
- Bind to H+ when pH drops
- Release H+ when pH rises
Three major chemical buffers
- Bicarbonates
- Phosphates
- Proteins
Buffering SystemsBuffering Systems
DevelopmentalDevelopmental Control of voluntary sphincter ~ 18 mos
Urinary infections - common problems
Bladder shrinks
Decline in function
Retention if prostate enlarges (males)
AgingAging
Fetal/NewbornFetal/Newborn Functional kidneys by 3rd month
Bladder is small in newborn
Urine cannot be concentrated
Recommended