week 9 Flashcards
what are the organs of the urinary system and their functions?
Organs include:
– kidneys (2) - major excretory organs
– ureters (2) - transport urine from
kidneys to urinary bladder
– urinary bladder - temporary storage
reservoir for urine
– urethra - transports urine out of
body
where is urine produced and where does it flow?
- Urine is produced in the kidneys then flows down the
ureters to the bladder and to the outside via the urethra
what do kidneys filter?
Kidneys filter the blood and remove wastes and excess
water and electrolytes by producing urine
what is Excretion ?
- Excretion - separation of wastes from body fluids and
their elimination outside the body
what do kidneys excrete?
- Excretion of wastes & foreign substances (e.g. drugs)
what do kidneys regulate?
- Regulation of blood ionic composition: Na+, K+, Ca2+, Cland phosphate (PO3−
4) ions - Regulation of blood pH by removing excess of H+ (acids)
or bases (HCO3-) from blood; kidneys have almost
unlimited capacity to regulate blood pH unlike blood buffer
systems - Regulation of blood volume - conserving or eliminating
waste - Regulation of blood pressure via secretion of enzyme
renin and activation of angiotensin-aldosterone system
what is stimulated by kidneys?
Stimulation of erythrocyte formation in the bone marrow
by releasing hormone erythropoietin (EPO)
what do kidneys activate?
Activation of vitamin D (together with liver)
what is the shape and size of the Kidneys
Paired bean-shaped organs: 10-12cm long, 5-7cm wide, 2cm thick
location of kidneys
Located between the parietal peritoneum and posterior wall of
abdomen – retroperitoneal organ
- Right kidney is located lower than left due to the liver occupying
space in the upper right abdomen
where do blood vessels etc enter in kidney?
- Blood vessels, nerves and ureter enter hilum of kidney on the
concave medial border
anterior view of kidneys diagram
what is the External Anatomy of Kidneys
- Parietal Peritoneum covering ant. aspect of kidney
- Renal fascia - the anchoring outer layer of dense fibrous connective
tissue - Perirenal fat capsule - a fatty cushion
- Thin fibrous capsule (outermost layer of the kidney)
what is the Internal Anatomy of Kidneys
- Renal cortex = superficial layer of kidney covered by
renal/fibrous capsule (capsule = thin connective tissue layer) - Renal medulla = inner portion
consisting of several coneshaped renal pyramids
separated by renal columns
– tip of pyramid is called renal
papilla; opens into a minor calyx - Renal sinus = cavity that
houses the initial segment of the
urine drainage system
– cuplike structure (minor calyces)
collect urine from the papillary ducts
of the papilla
– minor calyces drain urine into major calyces which then empty into renal
pelvis which in turn empties into ureter
what type of blood enters the kidney and via what?
- Oxygenated, unfiltered
blood from the
abdominal aorta enters
the kidney (at the
hilum) via the renal
artery
what does blood entering kidney supply and what is it filtered by?
– supplies kidney tissue
– filtered by the kidney
what type of blood leaves the kidney and via what?
Deoxygenated, filtered
blood leaves the kidney
(at the hilum) via the
renal vein which drains
into the IVC
veins and arteries in kidney diagram
where does the kidney receive sympathethic information from?
- Kidneys receive
sympathetic
information from
the renal plexus
what does The sympathetic
nervous system
trigger?
r vasoconstriction
and reduce renal blood
flow
There is no evidence of
……. ……..
supplying the kidney
parasympathetic fibres
diagram of nerve supplies of the kidney
how much fluid is processed by the kidney daily?
180 L fluid processed daily; only 1.5 L urine
how much plasma do the kidneys filter?
- Kidneys filter body’s entire plasma volume 60
times each day
what are the Three processes in urine formation and adjustment
of blood composition
Three processes in urine formation and adjustment
of blood composition via nephrons
– Glomerular filtration: produces cell- and protein-free
filtrate
– Tubular reabsorption: Selectively returns 99% of
substances from filtrate to blood in renal tubules and
collecting ducts
– Tubular secretion: Selectively moves substances from
blood to filtrate in renal tubules and collecting ducts
contents of urine
– <1% of original filtrate
– Contains metabolic wastes and unneeded substances
what is a Nephron?
Functional unit of the kidney that filters blood and produces urine
how many nephrons does each kidney have?
Each kidney has around 1 million nephrons
where are nephrons located?
- Located in the cortex and medulla
nephron composition
Composed of two parts: renal corpuscle and renal tubule
function of renal corpuscle
- Renal corpuscle = site of
plasma filtration
– glomerulus –> capillaries where
filtration occurs
– glomerular (Bowman’s) capsule
–> double-walled epithelial cup
function of renal tubule
- Renal tubule = transport,
reabsorption and secretion
– proximal convoluted tubule
– loop of Henle
– distal convoluted tubule
where do nephrons drain into?
All nephrons drain into
collecting ducts (many into
one)
Blood Supply and Drainage of
Nephrons diagram
Blood Supply and Drainage of
Nephrons diagram continued
Kidneys account for only …..%
of body weight
0.5%
how much of the cardiac output do kidneys receive?
they receive
about 20% of the cardiac
output (CO = HR x SV)
what does Renal artery divide into?
Renal artery divides into
segmental arteries that give
rise to:
- interlobar arteries - up renal
columns, between pyramids
- arcuate arteries - over pyramids
- interlobular arteries - up into
cortex
- branch into afferent arterioles -
each supplying one nephron
Blood is drained from the
glomerulus by ………
efferent arterioles which lead to either
peritubular capillaries (around
convoluted tubules) or vasa
recta (around loop of Henle)
where does vasa recta drain into?
vasa recta drain into interlobular
veins or directly into arcuate
veins
where do interlobar veins drain into?
- Interlobar veins drain into
renal vein and then empty into
inferior vena cava
Blood Supply and Drainage of
Nephrons diagram
what is Glomerulus and where does it arise from?
Glomerulus is a tuft-like capillary network arising from
the afferent arteriole
where does all blood from glomerular capillaries go into?
All blood from glomerular capillaries goes into efferent
arteriole (no exchange of gases blood is still
oxygenated at the end of the capillary network)
diagram of the renal Corpuscle
what layers is the bowman’s (glomerular) capsule made of and what is between them?
Bowman’s (glomerular) capsule has two layers
(parietal and visceral) – in between is capsular
space; extends into proximal convoluted tubule
what is Visceral layer of the capsule composed of ?
Visceral layer of the capsule is composed of epithelial
cells called podocytes that cover outer surface of the
glomerular capillaries
describe the 3 basic processes Nephrons perform?
- Nephrons perform 3
basic processes
1. Glomerular filtration:
filtration of blood plasma
components and formation
of glomerular filtrate
2. Tubular reabsorption:
water, electrolytes and
nutrients are reabsorbed
back into the blood
3. Tubular secretion:
some wastes (ammonia,
some medications) are
actively secreted into urine
from blood
diagram of m 3
basic processes nephrons perform
what does Blood hydrostatic pressure in glomerulus (GHP) produce? and what type of process is this?
Blood hydrostatic pressure in glomerulus (GHP)
produces glomerular filtrate (water and small solutes,
no cells or plasma proteins)
- passive process (as no
energy used)
what is the Filtration membrane ?
fenestrated capillary
endothelium, basement membrane of the capillary and
podocytes
How much Glomerular Filtrate is produced daily?
150-180 L/day of filtrate produced but most
reabsorbed – only 1-2 L of urine excreted
what is Glomerular filtration assisted by?
- Glomerular filtration is assisted by:
– large surface area of glomerular capillaries for filtration
– thin and porous filtration membrane (endothelial cells in
capillaries have numerous pores – fenestrations)
Glomerular Filtration process?
- GHP forces fluids and solutes through filtration
membrane and is opposed by glomerular capsule
osmostic pressure (GCOP) and capsular hydrostatic
pressure (CHP)
what is Glomerular Filtration Rate (GFR)?
Volume of filtrate formed per minute by both kidneys (normally ~ 120 -125 mL/min)
what is GFR directly proportional to?
– Net Filtration Pressure – primary pressure is
blood hydrostatic pressure in glomerulus (GHP)
– Total surface area available for filtration – which
glomerular mesangial cells can control by
contracting
– Filtration membrane permeability
why is Glomerular Filtration Rate (GFR) mandatory for kidneys?
Constant GFR allows kidneys to make filtrate
and maintain extracellular homeostasis
what is the Goal of intrinsic controls?
maintain GFR in kidney
what does GFR affect?
GFR affects systemic blood pressure
– Increased GFR = increased urine output = lowered blood pressure, and
vice versa
what is the Goal of extrinsic controls ?
maintain systemic blood
pressure
where must Glomerular Filtrate continue through?
The filtrate must continue through the
proximal convoluted tubule, Loop of
Henle and distal convoluted tubule
where nutrients & ions are reabsorbed
into the blood and wastes & ions are
secreted into the filtrate
what is reabsorbed and secreted in the proximal convuluted tubule?
– R: H2O, Na+, HCO3−, Glucose, amino acids, etc.
– S: H+, NH4+, some drugs, etc.
what is reabsorbed and secreted in the Loop of Henle?
– R: H2O, Na+, K+, Cl-
– S: Urea
what is reabsorbed and secreted in the Distal convoluted tubule?
– R: Na+, Ca2+, Cl-
– S: K
diagram of Tubular Reabsorption
and Secretion of filtrate
What happens to Antidiuretic hormone (ADH) during Tubular Reabsorption
and Secretion?
– released by post. part of pituitary gland
– increases water reabsorption in the
collecting ducts
What happens to Aldosterone during Tubular Reabsorption
and Secretion?
– secreted by the adrenal glands
– acts on collecting ducts and distal
convoluted tubules
– Na+ reabsorption –> water follows
– decreases K+ levels
What happens to Parathyroid Hormone during Tubular Reabsorption
and Secretion?
– secreted by the parathyroid glands
– acts on distal convoluted tubule
– increases Ca2+ reabsorption
diagram of Countercurrent Multiplier
what is Renal Autoregulation?
the ability of the nephrons to adjust
their own blood flow and GFR without external (nervous or
hormonal) control.
Autoregulation ceases when….
MAP (mean arterial pressure) is below 80 mmHg
what are the Two mechanisms of autoregulation?
Myogenic mechanism and Tubuloglomerular feedback
what is Myogenic mechanism?
- based on the tendency of smooth
muscle to contract when stretched - Increased arterial blood pressure stretches the afferent arteriole which
stimulates muscle cells to contract - When blood pressure falls, the afferent arteriole relaxes and allows blood
flow more easily into glomerulus - Filtration remains stable
what is Tubuloglomerular feedback?
- mechanism by which
glomerulus receives feedback on the status of the downstream
tubular fluid - Juxtaglomerular apparatus: a structure where afferent arteriole makes
contact with ascending limb of loop of Henle (or distal convoluted tubule) - Tubule comes into contact with the afferent and efferent arterioles at the
vascular pole of the renal corpuscle
what are Granular cells?
enlarged, smooth muscle cells with
secretory granules containing renin. They are
mechanoreceptors that sense changes in BP in aff.
arteriole.
what is Macula densa?
is a group of tall, closely packed cells that
lie adjacent to the granular cells. They are chemoreceptors
that respond to changes in the solute content of the filtrate.
They release paracrine signals that stimulate granular
cells.
Both cells are
sensors in a
feedback loop
that controls
GFR and
systemic BP. what cells are they referring to?
Granular cells and mascula densa known as Juxtaglomerular Apparatus
what are Mesangial cells ?
Mesangial cells are located in the cleft between afferent
and efferent arterioles, and among capillaries of the
glomerulus.
what are mesangial cells connected to?
They are connected to macula densa and granular cells by
gap junctions and communicate with paracrine substances.
what do mesangial cells form?
Form a supportive matrix for glomerulus, constrict and relax
capillaries to regulate blood flow.
what are Ureters?
muscular
tubes that transmit
urine from kidneys to
bladder
what is Bladder?
muscular sac
for temporary storage
of urine
what is bladder innervated by?
Innervated by the
parasympathetic
nervous system via
sacral nerves
where is the bladder located?
Retroperitoneal, on
pelvic floor posterior to
pubic symphysis
* Males - prostate
inferior to bladder neck
* Females - anterior to
vagina and uterus
diagrams of Ureters and Urinary Bladder
what are the Layers of bladder wall ?
- Mucosa - transitional epithelial mucosa
- Thick detrusor m.- three layers of smooth muscle
- Fibrous adventitia (peritoneum on superior
surface only)
what is the Trigone?
- Smooth triangular area
outlined by openings for
ureters and urethra - Infections tend to persist in
this region
what happens when bladder is empty?
Collapses when empty;
rugae appear
how long is a full bladder and what capacity can it hold?
Full bladder is 12 cm long;
holds ~ 500 ml
* Able to hold twice that if
necessary (can burst if
over-distended)
what is Urethra?
Muscular tube draining urinary bladder
what is Internal urethral sphincter?
– Involuntary (smooth muscle) at bladder-urethra junction
what is External urethral sphincter?
Voluntary (skeletal) muscle surrounding urethra as it passes through
pelvic floor
size of Female urethra
(3 - 4 cm)
location and position of female urethra
- Tightly bound to anterior
vaginal wall
– External urethral orifice - Anterior to vaginal opening
- posterior to clitoris
how long is male urethra?
Male urethra (19 - 20 cm)
what does male urethra carry?
Carries semen and urine
what are the Three named regions of the male urethra?
Three named regions:
* Prostatic urethra (2.5 cm)
within prostate
* Membranous urethra (2
cm) passes through
urogenital diaphragm from
prostate to beginning of
penis
* Spongy urethra (15 cm)
passes through penis; opens
via external urethral orifice
sagittal sections of urethras
what is Micturition?
Urination or voiding
what Three simultaneous events must occur for micturition
– Bladder distension activates contraction of
detrusor by sacral nerves (parasympathetic)
– Opening of internal urethral sphincter by
sacral nerves
– Opening of external urethral sphincter by
somatic nervous system (voluntary)
Micturition is __________.
voiding urine
The most important factor affecting the glomerular filtration rate is __________.
net filtration pressure
The basic functional unit of the kidney is the __________.
nephron
The Bowman’s capsule and glomerulus make up the __________.
renal corpuscle
The blood supply to the renal corpuscle is the __________.
The Afferent Arterioles (which are small branches from the interlobular arteries) feed blood into the renal corpuscle.
This blood is unfiltered and is forced into the glomerulus, where it undergoes filtration.
The filtered blood then exits the renal corpuscle via the Efferent Arteriole.
All of the following functions are carried out in the renal tubules, EXCEPT __________.
filtration
Which substance would not normally be expected in urine?
protein
All of the following are layers of the filtration membrane in the glomerular membrane, EXCEPT the __________.
a.
visceral layer
b.
basement membrane
c.
fenestrated endothelium
d.
renal capsule
renal capsule
a. detrusor muscle
b: external urethral orifice
c: right ureter
d: urethra
a: renal pyramid
b: renal column
c: renal pelvis
d: minor calyx
e: ureter
a: Interlobular artery/Cortical Radiate artery/Radiate artery
b: Arcuate artery
c: Interlobar artery
d: Segmental Artery
e: Renal Artery
a: detrusor muscle
b: spongy urethra
c: right ureter
d: internal urethral sphincter
e: prostatic urethra
f: Membranous Urethra/External urethral sphincter
a: Renal Papilla
b: Renal Pelvis
c: Arcuate vein
d: Renal Pyramid
e: Major calyx
a: Right suprarenal gland/Right adrenal gland
b: Right renal vein
c: Right ureter
d: Left kidney
e: Left renal artery
The 3 openings that contribute to the trigone in the bladder are the:
- Left ureteric orifice
- Right ureteric orifice
- Internal urethral orifice
The kidneys are considered as ….. structures.
The kidneys are retroperitoneal structures as they are located behind the peritoneum.
the correct sequence of layers in the kidney, starting from the most superficial layer?
Renal Capsule, Renal Cortex, Renal Medulla, Urine Drainage System
What are the muscular folds located in the bladder called?
Rugae
The renal arteries arise
from the _________
The renal veins drain into
the _________
Aorta
Inferior vena cava
The bladder is a/n:
intra / inter / retro –
peritoneal structure
Retro- peritoneal
Antidiuretic (ADH)
hormone makes the body ….. water
retain
The external urethral
sphincter is controlled …..
voluntarily
List the 3 specialised cell
types that are located in
the juxtaglomerular
complex
Macula Densa
Granular cells
Mesangial cells
Name the storehouse for
sperm
Epididymis
Where is the prostate
located in relation to the
bladder
Inferior to the bladder
Name the hormone that is
produced in the testes that
initiates spermatogenesis
Testosterone
List the 3 layers of the
uterine wall (inside –>
outside)
Endometrium,
Myometrium and
Perimetrium
Which hormone/s does the
Corpus Luteum secrete?
oestrogen and
progesterone
