HUBS192 Lecture 28-34 URINARY SYSTEM

how much water is the male and female body made of? why is this difference?

male - 60%

female - 55%

males have more muscle mass which contains more water

what is urine? describe normal urine and abnormal urine

waste product excreted to maintain balance within the body

normal = water, salts, hormones, small proteins

abnormal = large proteins, RBCs, glucose

what are the major organs of the urinary system? how many of each?

2 kidneys, 2 ureters, urinary bladder and urethra

what is the function of the kidneys?

• protection

• storage

• filtration

where are the kidneys located? what protects the kidneys?

between T12 and L3

11th and 12th ribs

where do the renal blood vessels, lymphatics, nerves and ureter enter the kidneys?

hilum

what kidney is closer to the aorta?

left

what are the 3 regions of the kidney?

cortex, medulla, pelvis

what is at the end of each medullary pyramid?

papilla

how many lobes are there per kidney?

5-11 lobes

urine drains from each papilla and collects where?

calyx

what joins to make the renal pelvis?

calyces

how is urine produced?

filtering waste from the blood into the nephron

where does filtration occur?

in the cortex of the kindey —> glomerular capillaries

what arteriole delivers blood from the arteries to the glomerulus?

afferent arteriole

what is the golmerulus made of?

glomerular capillaries

Where does the efferent arteriole carry blood from and to?

from glomerulus to pertitubular capillaires

where do the peritubular capillaries carry blood to?

the veins

In what order does the bloody supply get into the cortex to be filtered?

renal artery > series of ateries > afferent arteriole > glomerular capillary

In what order does the bloody supply get away from the cortex after being filtered?

efferent arteriole > pertibular capillaries > series of veins > renal veins > inferior vena cava

what 3 things does the nephrphron do?

1. filters blood

2. selectively reabsorbs or secretes

3. produces urine

how many nephrons are there per kidney?

1 million

what are the 2 types of nephrons and describe them

cortical - 85%, lie mainly in cortex

juxtamedullary - deep in medulla- conc urine

what is the function of nephrons?

• filter blood

• carry waste away

what 3 things is each nephron comprimised of?

• glomerular capsule

• renal tubules

• collecting duct

what is the function of glomerular capillaries? what type of endothelial cells does it contain?

• filtration

• fed and drained by arterioles

fenestrated endothelial cells

what is the function of peritubular capillaries?

• specialised for absoprtion

• wrap around ranl tubules

• receive filtered blood and reabsorbed filtrate

what nephrona are found in extensions that follow nephron loops deep into the medulla?

vasa recta

what is the renal corpuscle made of?

glomerulus enclosed by the glomerular capsule

• where capillary and nephron meet

• site of filtration barrier

what are the two layers of the glomerular capsule? what are they made of? what is found between these two layers?

1. outer parietal layer - simple squamous cells

2. inner visceral layer - podocytes

capsular space

where are podocytes located? what do the branches coming off them form?

around the glomerular capillaries

pedicels

what is found between the pedicels? what passes through these slits?

filtration slits

filtered blood passes through into capsular space

where does the filtration barrier lie? what does it allow for?

between blood and capsular space

allows free passage of water and small molecules but not proteins

what are the 3 layers of the filtration barrier?

1. fenestrated endothelium of glomerular capillary

2. fused basement membrane

3. filtration slits between the pedicels of the podocytes

What is the function and structure of the proximal convoluted tubule?

• for bulk reabsoprtion

• surround by peritubular capillaries

• cuboidal epithelial cells, desnse microvilli, highly folded basolateral membrane, mitochondria for transport, leaky epithelium

What is the function and structure of the distal convoluted tubule?

• fine tuning

• cuboidal but thinner than PCT

• fewer mitochondria

• fewer microvilli

• influenced by aldosterone

what is the nephron loo surrounded by

vasa recta

describe the structure of the thick and thin descending limb and thick and thin ascending limb

thick descending - cuboidal epithelium

thin descending - simple squamous epithelium

thick ascending - simple squamous epithelium

thin ascending - cuboidal but thinner

what is the structure of the colelcting duct?

wall of simple cuboidal epithelium

principal cells - reabsorption

intercalated cells - acid/base balance

what is reabsorption influenced by in the collecting duct?

aldosterone / ADH

what is transitional epithelium?

• stratified rounded cells

• flattened when stretched

• for protection

• connected by tight junctions

where do the ureter arise from? where do they descend

each renal pelvis at each hilum

retroperitoneally through the abdomen , vertically from the hila

what do peristaltic waves do?

move urine to bladder

what is the ureter made of? what 3 layers does it consits of?

smooth muscle and CT

1. transitional epithelium

2. muscularis (inner longitudianl, outer circular)

3. adventitia

the ureter prevents backflow? true or false?

true

what is the function of the urinary bladder?

• stores and expels urine

describe what an empty bladder would look like?

• pyramidal

• lies within the pelvis

describe what a full bladder would look like

• spherical

• expands superiorly

• can be palpated above the pubic pymphysis

where is the location of the bladder in males and females?

males - anterior to rectum, superior to prostate gland

females - anterior to vagins and uterus

describe detrusor muscle

• thick smooth muscle

• longitudinal, circular, oblique

• expels urine

• forms the wall of the bladder

what does the trigone area consist of?

2 openings of entry of ureter and 1 opening for urethra

what is the role of the urethra? In what order does the epithelium go? where is there mucus glands in the urethra?

drains urine from the bladder out of the body

transitional, columnar, stratified squamous

protect epithelium from urine

what are the differences between male and female urethras?

males = longer (25cm), part of reproductive system

• 3 sections = prostatic, membranous, spongy/penile

females = shorter (5cm)

describe the internal and external urethral sphincter

internal

• junction of bladder and urethra

• detrusor muscle - involuntary control

external

• located where urethra passes through the urogenital diaphragm

• skeletal muscle - voluntary control

descrieb the process of urination

• bladder fills with urine and expands

• AP from stretch receptors to brain

• urgency increases as signal increases

• internal sphincter relaxes

• conscious relaxation of external sphincter

what are the 2 endocrine functions of the kidney? describe them?

erythropoietin (EPO)

• low oxygen levels detected by the kidney

• kidneys release EPO - produces more RBCs

chronic kidney/renal failure

• kidneys cannot produce enough EPO

• reduced RBC production

• Anaemia

what is a metabolic function of the kidney? when does this process happen

gluconeogenesis

• during fasting or when our body is under stress

• kidneys make glucose from lactate

The more H+ ions there are the ________ the PH = more________

lower

acidic

The PH of blood is controlled by what 2 things?

• lungs - exhalation of CO2

• kidneys - reabsorption and secretion of bicarbonate and hydrogen

what is excreted in the kidneys after metabolism in the liver due to its fat soluble nature?

lidocaine

what pain killer is excreted directly by the kidnyes due to its high water solubility (hydrophillic)?

Aspirin

what are the 3 basic functions of the nephron?

1. filtration

2. secretion

3. reabsorption

where does filtration occur in the nephron? what is its function?

occurs in the renal corpsucle/glomerus

movement of blood from glomerulus capillaries into glomerular capsule

what 2 things are not filtered in plasma?

large proteins and substances bound to proteins

what is secretion in the nephron? what is its function?

movement of solutes from the peritubular capillaries into tubular fluid

removes waste from blood by excreting them into tubular fluid into urine

what is the function of reabsorption in the nephron?

movement of solutes from tubular fluid into peritubular capillaries

returns substances to the blood so they are not excreted

what 3 things determine glomerular filtration?

• filtration barrier

• renal blood flow

• driving forces

what are the 2 types of driving forces of glomerular filtration? describe these

1. hydrostatic pressure - pressure due to the volume of fluid (Pushes fluid away)

2. colloid osmotic pressures - osmotic pressure due to protein (pulls fluid towards)

what are the 4 forces of glomerular filtration? describe them. what do these 4 pressure determine?

1. glomerular hydrostatic pressure = blood pressure

2. blood colloid osmotic pressure = albumin

3. capsualr hydrostatic pressure = pressure of filtrate already present

4. capsular colloid osmotic pressure = no protein in capsualr space

net filtration pressure

what is the filtration factor?

glomerular filtration rate / renal plasma flow

how much plasma is filtered by the kidney per day and per minute? how much urine is produced a day?

per day = 180L

per minute = 125ml

urine = 1.5L

what is the equation for filtered load?

GFR x solute plasma conc

what is renal clearance and what is it used for?

• the volume of plasma that is cleared of a substance by the kidneys

• estimate GFR

what is glomerular filtration rate described as?

amoutn of plasma filtered per unit time by the kidneys

to be sued to measure GFR a substance must? what 2 substances meet this criteria and why?

be freely filtered, not be reabsorbed, not be secreted

• inulin - not found in body

• creatinine - waste product produced by muscles, used clinically

When is plasma creatinine low?

when both kidneys are working

what 3 places is water reabsorbed in the nephron?

• PCT

• descending limb of loop

• DCT

• collecting duct

describe bulk and regulated water reabsorption

Bulk

• not regulated

• leaky epithelia

• 92% of total reabsorption

regulated

• regulated by ADH

• tight epithelia

• only transcellular reabsorption

what is reabsorption of sodium into the nephron regulated by?

aldosterone

what is water reabsorption driven by in the Proximal tubule? what is transported through the proximal tubules?

Na+ reabsorption

glucose and sodium

where does chloride flow through in the proximal tubule?

paracellular pathway

what is the ascending and descending limb permeable to?

ascending = sodium

descending = water

where does the ascending loop reabsorb Na+ into?

the peritubular fluid

Describe the difference between normal urine and pathological urine

normal

• 1.5 L a day

• H+, k+, Na+

• medications, toxins

pathological

• blood

• organge

• sweet - diabetes

• fruity - ketones forming

• rotten - infection, tumour