Anatomy Test 4 (Final!) Flashcards
The Urinary System
kidney
ureter
urinary bladder
urethra
The Urinary System: Kidney
produces urine
The Urinary System: Ureter
transports urine toward the urinary bladder
The Urinary System: Urinary Bladder
temporarily stores urine prior to elimination
The Urinary System: Urethra
Conducts urine to exterior
Drinking water absorption by GI Tract
To where?- blood
Then to where?- renal arteries supply kidneys
Becomes what?- urine
nephron what is left empties into collecting system
reabsorption, filtration, excretion
Functions of the Kidneys (1)
Excretion:
-removal of wastes from body fluids in urine
Regulation of Blood:
- ions: control blood NA+, K+, and Cl- levels
- pH: control blood H+ and HCO3- levels
- pressure and volume: control blood fluid volume and thus blood pressure
Functions of the Kidneys (2): Kidneys accomplish this by three processes
- filtration of water, ions, nutrients and waste products from the blood
- reabsorption of most of the water, ions and nutrients back into the blood
- excretion of metabolic wastes into the urine
The Kidneys are our heros!
- “Insensible” water loss is occurring as I speak and you breathe!
- We lose water constantly though our: skin, lungs, digestive system
- The Kidneys can regulate water volume in our bodies because they can: Concentrate or dilute the urine
- The Kidneys are responsible for our ability to survive on land without dehydration!
The Position of the Kidneys
The kidneys are located:
- on either side of the vertebral column
- partly protected by the rib cage
The divisions of the Kidney
- Renal cortex: outer portion of kidney
- renal medulla: inner portion of kidney, separated into renal pyramids by renal columns
Blood Supply to the Kidneys
-Each kidney receives blood from a renal artery
It branches into many smaller and smaller arteries which…
- travel between renal pyramids within the renal column s and
- ultimately deliver blood via arterioles to a capillary network called “glomerulus”
Facts about the Blood Supply to Kidneys
- Kidneys receive 20-25% of total cardiac output
- 1.2 liters of blood flows through kidneys each minute
- The entire blood volume is filtered by the kidney 60 times/day
- If the blood filtered by the kidney were entirely excreted, your entire blood volume would be excreted in 25 minutes
- (99% of the filtered blood is actually returned to the cardiovascular system)
Kidney Histology
- The Kidney is composed of: nephrons and a collecting system
- The Kidney contains about 1.25 million “nephrons” (85 miles in combined length)
The Nephron
-The Nephron is the functional unit of the kidney
Urine production begins in the nephron
- blood is filtered into the nephron
- composition changes during the process
Composed of: Renal corpuscle and renal tubule
Renal corpuscle: Spherical structure is composed of
- Glomerulus
- Bowman’s capsule
- Urinary Space
Renal Corpuscle (2): Glomerulus
- Glomerulus: intertwining network of capillaries
- receives blood from the afferent arteriole
- blood leaves through the efferent arteriole
Renal Corpuscle (3): Bowman’s capsule
- Composed of squamous epithelial cells
- Sac-ike structure surrounds the glomerulus encloses the urinary space
Renal Corpuscle: Urinary Space
-space between the inner layer lining of the glomerulus and the outer layer of the capsule
Filtration of fluid from blood into the nephron
- Occurs in the ventral corpuscle
- Blood pressure forces H2O and dissolved substances out of the glomerulus into the urinary space
- produces a protein free solution called filtrate similar to blood
Three layers of filtration
- ) The Glomerulus (capillary): endothelial call layer
- ) Middle connective tissue layer
- ) Inner lining of the Bowman’s capsule: epithelial cell layer
The role of the glomerular endothelial layer
- Specifically, there are pores, in the endothelial cells lining the glomerular capillaries
- They are small enough that they prevent passage of blood cells into the filtrate
- But they do allow some proteins to get through
The role of the podocyte layer of the inner lining of Bowman’s capsule (1)
- However, the glomerural capillaries are surrounded by epithelial cells “foot cell” called podocytes of the inner lining of Bowman’s capsule
- composed of many foot processes called pedicles
The role of the podocyte layer of the inner lining of Bowman’s capsule (2): Filtration slits
- Filtration slits (narrow gaps) between adjacent pedicles of podocyte
- smaller than the pores of the endothelial cells
- they only allow H2O and dissolved solutes from the blood into the urinary space
Blockade of the middle connective tissue layer induces kidney disease
1) endothelial cells (pores)
2) connective tissue
3) podocyte cell (slits)
- The connective tissue layer between the pores and slits can become clogged with “debris”!
- This leads to kidney disease and to kidney failure!
Renal Tubule (1)
-a long U-Shaped tube extending from the cortex into the medulla and back to the cortex
Renal Tubule (2): structures that make up this
-It begins at renal corpuscle
- It is composed of the:
- proximal convoluted tubule (PCT)
- loop of Henle
- distal convoluted tubule (DCT)
It ends at the collecting duct
Composition of the wall of the tubule
- The wall of the renal tubule is composed of epithelial cells:
- from squamous
- to columnar
- depending on the degree of activity of that portion of the tubule
Return of Filtrate from the nephron back into the blood (1): Functions
- Functions of renal tubule cells:
- reabsorb nutrients from the filtrate
- return them to the blood
- reabsorb water (90%) from filtrate
- return it to the blood
- what is left in the tubule is excreted in the urine
- filtrate traveling along the tubule composition changes
Peritubular capillaries and vasa recta
-The reabsorbed H2O and solutes returns from the filtrate in the tubule to the blood via
- Pertibular capillaries
- Vasa rectal
- both are branches of efferent arteriole (so leaves kidney)
- they drain blood into the venous system and back to the heart
What does PCT stand for?
Proximal convoluted tubule
The PCT (proximal convoluted tubule)
- The 1st segment of renal tubule
- bulk reabsorption of filtrate occurs here:
- 60-70% of the filtrate is reabsorbed here: epithelial cells have microvilli to increase surface area for absorption
The loop of henle
-Middle segment of the renal tubule
Composed of a:
- descending limb, fluid flows “down” into the medulla
- ascending limb, fluid flows “back up” into the cortex
How the Loop of Henle Concentrates Urine
- Na+ and Cl- are actively pumped out of the ascending limb (and back into the bloodstream)
- H2O follows out of the descending limb (and back into the bloodstream)
- tubular fluid becomes very concentrated
- urea
Urea
- the most abundant organic waste from amino acid breakdown
- is now the main solute left in the tubular fluid, hence “urine”
The DCT (distal convoluted tubule) (1)
-Last segment of the renal tubule
Note that the epithelial cells lining the DCT:
- are smaller than those of the PCT and do NOT have microvilli
- these cells are less active than the cells of the PCT
- but these cells are more highly specialized than the cells of the PCT
What does DCT stand for?
distal convoluted tubule
The DCT (distal convoluted tubule) (2)
- further adjustment to the filtrate are made in the DCT
- very selective reabsorption occurs here in response to hormones
- to regulate blood pressure and volume, blood pH
A word about the Real anatomy of the Nephron
- Let’s return to the renal corpuscle and related structures…
- First, it is important to note that the DCT is related to the renal corpuscle like this
- Not this
Look at PG. 106
The Juxtaglomerular apparatus
This is an endocrine structure composed of:
- Macula densa: specialized epithelial cells in the DCT
- Juxtaglomerular JG cells: specialized smooth muscle cells of the afferent arteriole
What does juxta mean?
close to
How the DCT regulates blood pressure and volume (1)
- if decreased blood pressure is sensed by the JG cells
- the JG cells release renin (a hormone)
- renin activates angiotensin (another hormone)
What does JG stand for?
juxtaglomerular apparatus
How the DCT regulates blood pressure and volume (2): angiotensin
Angiotension
- Causes: vasoconstriction (look at its name!)
- and secretion of aldosterone (a mineralcorticoid hormone) by the adrenal cortex
(increased BP)
How the DCT regulates blood pressure and volume (3): Aldosterone
Aldosterone
Causes DCT cells:
-raise Na+ reabsorption (both always follows Na+)
-Both are returned to the blood
-This raises blood pressure and raises blood volume
How the DCT regulates blood pressure and volume (4)
- If increase blood pressure or volume is sensed by stretch receptors of the heart walls, atria of the heart releases atrial natriugetic peptide (ANP hormone)
- causes decrease in Na+ (and H2O) reabsorption at the DCT so raises Na+ (and H2O) excretion into the urine
- results in decrease BP and volume
What does Natrium mean?
sodium
What does natriuresis mean?
urinary excretion of sodium
Summary of DCT
- decrease blood pressure leads to:
- renin-> angiotensin->aldosterone
- raises Na+ and H2O reabsorption at DCT
- raises blood volume and therefore pressure
- less water in the urine
- urine becomes more concentrated
- raises blood pressure leads to:
- ANP->
- decrease Na+ and H2O reabsorption at DCT
- decrease blood volume and therefore pressure
- more water in the urine
- urine becomes more dilute
How the dCT regulates blood pH
The DCT controls blood pH by both
- H+ excretion into the forming urine
- HCO3- (bicarbonate) production and reabsorption into the blood
- HCO3- buffers the blood
The Collecting Ducts
- determine final urine composition and volume
- hypothalmic neurons are stimulated by decrease blood pressure or increase blood Na+/Cl- concentration:
- they release ADH (antidiuretic hormone): causes increase H2O reabsorption at the collecting duct
Collecting system: Collecting duct
variable reabsorption of water and reabsorption or secretion of sodium, potassium, hydrogen, and bicarbonate ions
Collecting system: Papillary duct
delivery of urine to minor calyx
Summary of how 2 important hormones increase blood pressure and volume
- aldosterone binding here causes Na+ reabsorption (H2O follows)
- ADH binding here causes only H2O reabsorption
collecting duct
Overview of the functions of the Components of the Nephron and Collecting Duct
Proximal convoluted tubule-bulk reabsorption Renal corpuscle-filtration Distal convoluted tubule-fine toning Collecting duct-hormones fine tuning Loop of Henle-concentration
The Collecting System of the Kidney
- The filtrate continues to pass through the collecting duct where its final composition is determined
- collecting ducts converge to empty into a minor calyx, which ends at the renal papilla of each renal pyramid
The Renal Calyces and Pelvis: Minor Calyx
- cup-like structure surrounding each renal pyramid
- collects urine from each renal __pg 108____
- several join to form a major calyx
The Renal Calyces and Pelvis: Major Calyx
- collects urine from several minor calyces
- join to form the renal pelvis
The Renal Calyces and Pelvis: Renal Pelvis
-acts as a funnel to drain urine from the kidney to the ureter
Urine Transport, Storage, and Elimination
-Takes place in the urinary tract: ureter, urinary bladder, urethra
Ureter- transports urine toward the urinary bladder
Urinary Bladder- temporarily stores urine prior to elimination
Urethra- conducts urine to exterior
The Ureters
Muscular tubes (smooth muscle)
- collect urine from renal pelvis
- empties urine into the urinary bladder
Pass through bladder wall at an angle
- prevents back flow of urine
- flatten as the bladder filled with urine and when bladder contracts to void the urine
The Urinary Bladder
- hollow, muscular organ (smooth muscles)
- temporary reservoir por urine storage
- a full bladder can contain 1 liter of urine
Urothelium
- AKA transitional epithelium (a type of stratified epithelium)
- lines the urinary bladder and ureters
- composed of cells that are impermeable to water and can rearrange themselves an spread out as the bladder fills with urine
The Male Urethra
- The male urethra is 7 to 8 inches long
- Begins at the inferior pole of the bladder passes through the prostate gland and penis
The Female Urethra
- The female urethra is much shorter, 1 to 2 inches long
- Therefore, a female is prone to more frequent infections of urinary bladder than is the male
The external urethral sphincter
In Both Sexes:
- skeletal muscle surrounds the urethra
- (voluntary muscle) (under conscious control)
- relaxation permits microturition (urination)
