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Physiology > Urinary System > Flashcards

Urinary System Flashcards

1
Q

Name and Describe the two factors that determine blood flow

A

Two factors which determine blood flow is pressure and resistance.
Pressure is the blood flowing through the blood vessels from the heart creeping a pressure gradient.
Resistance is the constricted blood vessels will create a greater force for the flow of blood than the non-constricted blood.

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2
Q

What are the three filtration functions of the urinary system?

A
  1. Excretion – getting rid of waste from body
  2. Elimination
  3. Regulatory homeostasis – water this contributes to blood pressure
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3
Q

Function of the Kidneys

A

Functions of the kidneys

  • Stabilising blood Ph
  • Calcium- other nutrients filtrate through the blood, amino acids
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4
Q

Explain the three hormones that affect reabsorption and excretion of water and sodium in the collecting ducts

A

Aldosterone – produced in the adrenal cortex, stimulates the reabsorption of water and sodium ions in the kidney which results in increased blood pressure and volume

ADH – controls the amount of water lost in the urine, reabsorbing the water through cells into the blood

Atrial natriuretic peptide - which is produced by the heart, it opposes aldosterone -increase the amount of sodium lost, this affects the blood volume especially the water, so the blood volume will decrease because less sodium and the water will follow the sodium and more water lost

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5
Q

Homeostatic mechanisms do what?

A

regulate cardiovascular activity to ensure that the amount of blood flow through tissues (called tissue perfusion) is adequate to meet the demand for oxygen and nutrients. Homeostatic mechanisms operating at the local, regional, and systemic levels adjust blood flow through the capillaries to meet the demands of peripheral tissues. One of the homeostatic mechanisms is the baroreceptor reflex. The baroreceptor reflex is involved in the homeostatic regulation of blood pressure.

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6
Q

illustrate the role of the baroreceptor reflex when blood pressure is too high:

A
  • stimulates baroreceptor
  • sends information to the cardiovascular centre
  • sends commands to the effectors
  • heart, decrease cardiac output, and describe heart rate
  • smooth muscles in the artery, vasodilation and decrease peripheral resistance
  • this together forms decrease blood pressure which restores homeostasis
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7
Q

Major Functions of the Urinary System

A

Kidneys filter blood(plasma part) removing toxins, metabolic wastes, excess ions from circulation
Produces urine
Returns filtered nutrients and important ions back to blood

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8
Q

But what are the three main functions of the Urinary system?

A
  1. Excretion- removal of metabolic wastes from body fluids
  2. Elimination – discharge of these wastes from body
  3. Homeostatic regulation – of volume and solute concentration of blood
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9
Q

Homeostatic functions of urinary system

A
  • Essential to homeostatic regulation are the following functions
    1. Regulating blood volume and blood pressure
  • By adjusting volume of water lost in urine
  • Releasing erythropoietin (control of erythropoeisesi) and renin
    2. Regulating plasma ion concentrations
  • By controlling quantities of sodium, potassium, chloride and other ions lost in urine
  • Calcium ion level controlled through synthesis of calcitriol> inhibits release of calcitonin>maintenance of calcium homeostasis/bone integrity
    3. Helping to stabilise blood pH
  • By controlling loos of hydrogen and bicarbonate ions in urine
    4. Conserving valuable nutrients
  • By preventing their loos (e.g glucose, amino acids) while removing metabolic wastes (e.g urea, uric acid and creatinine)
    5. Assisting liver
  • In detoxification of positions and gluconeogenesis during prolonged fasting
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10
Q

Organs of the urinary system

A
  • Kidneys
  • Urinary tract
  • Ureters
  • Urinary bladder
  • Urethra
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11
Q

Function and Structure of the Kidneys

A

Function: Produce urine
Structure: Bean shaped – 10cm long, 5.5cm wide and 3cm thick, Retroperitoneal and Protected by lower part of rib cage and three layers of supportive tissue

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12
Q

Function of the Ureters?

A

Transport urine towards the urinary system

  • Part of muscular tubes
  • Transport urine from kidneys to bladder by peristaltic contractions of smooth muscle in walls
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13
Q

Function of the Urinary Bladder

A

Temporarily stores urine prior to urination

  • Hollow muscular organ
  • Distensible due to presence of transitional cells in bladder wall can contain 400-500 mL of urine
  • Starts as thick folds, expands to become pear shaped
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14
Q

Function of the Urethra

A

Conducts urine to exterior; in males, it also transports semen

  • Conveys urine from body
  • Longer in males 18-20cm and then females 3-5 cm
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15
Q

what are the three layers of supportive tissue in the kidneys?

A
  1. Renal fascia – which is a dense connective tissue – anchor kidneys to surround structures
  2. Perinephric fat capsule – fatty mass protects kidneys from trauma
  3. Fibrous capsule – transparent layer; protection from infection
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16
Q

Adrenal glands

A

Adrenal glands

  • Two triangle shaped endocrine glands
  • Make hormones, adrenaline, noradrenaline, cortisol and aldosterone
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17
Q

what are the three hormones the adrenal gland makes and their function?

A

Adrenaline and noradrenaline: involved in bodies stress response
Cortisol: influences metabolism, changing BGL, and slowing down immune system
Aldosterone: plays a role in controlling BP

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18
Q

Internal Anatomy of the kidneys include?

A 
Renal cortex 
Renal medullar 
Renal Pelvis 
Nephron 
Renal Corpuscle
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19
Q

Renal cortex?

A
  • Light coloured; outer granular region

- Contains nephrons

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20
Q

Renal Medullar?

A
  • Middle region
  • Contains 6-18 renal pyramids
  • Empty urine into minor calyx to major calyx (which has been formed by 4-5 minor calcyes)
  • Channels urine to renal pelvis
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21
Q

Renal pelvis

A
  • Inner region

- Drains urine into ureters

22
Q

Describe the blood supply to the kidneys?

A
  • Kidneys receive 20-25 percent of total cardiac output
  • About 1200 mL of blood flow through kidneys each minute
  • Each kidney receives blood through a renal artery > arterioles
23
Q

Describe the Nephrons

A
  • Functional and structural unit of the kidney
  • 1 million per kidney
  • Perform the processes to filter blood plasma and form urine
  • Consists of – renal corpuscle and renal tubule
24
Q

what are the two parts of the renal corpuscle

A

Bowmans capsule

Glomerulus

25
Q

What is the Bowmans capsule?

A

The Bowmans capsule surrounds the glomerulus capillaries

26
Q

What is the Glomerulus?

A
  • Afferent arteriole (receives) brings about 20% of blood into a nest of capillaries
  • Capillaries fenestrated and porous
  • Allows small solutes but not large proteins to pass from blood into the capsule to form a filtrate
  • Blood that has not become filtrate is returned to circulation via efferent arteriole
27
Q

What is the function of the renal corpuscle?

A

the function of the renal corpuscle is to produce the filtrate – a protein free solution (example, water, ions, nutrients) that resembles normal plasma but has no proteins and cells> enters renal tubule» forms urine to be excreted

28
Q

Renal corpuscle has…….

A
  • Special vessels transport blood to, in and away from the nephrons
  • An afferent arteriole (IN) delivers blood to each nephron where it enters the glomerulus for filtration; the glomerular capillaries are much more permeable than other capillaries
  • Glomerular capillaries merge to form an efferent arteriole (OUT)
  • The efferent arteriole splits to form the peritubular capillaries, which eventually carry filtered blood into venules and out of kidneys to be returned to systemic blood stream
29
Q

What are the renal Tubule main parts?

A
  1. Proximal convoluted tubule (PCT)
  2. Nephron loop (Loop of henle)
  3. Distal convoluted tubule (DCT)
30
Q

While traveling along tubule, the tubular fluid (protein free filtrate) gradually changes in composition to become urine due to……

A

valuable substances e.g. glucose being reabsorbed in various segments of renal tubule into peritubular capillaries that closely surround the tubule and then these substances are returned to systemic blood supply and, due to other waste substances e.g. excess hydrogen ions being secreted out of peritubular capillaries that surround the tubule back into the tubule, destined to be excreted as urine

31
Q

What is the renal tubule functions?

A
  1. reabsorb – useful organic nutrients that enter filtrate example all glucose and amino acids
  2. reabsorb more than 90% of water in filtrate
  3. secrete waste products example fine tuning to rid body of any unwanted ions in blood back into tubules for funeral excretion in urine.
32
Q

Basic process of urine formation

A
  • filtrate is modified as it passes through the tubule to become urine
    1. Glomerular filtration
  • makes a protein-free filtrate that contains water, ions, nutrients and waste products.
    2. Tubular Reabsorption
  • Selective movement of valuable wanted substances from, filtrate back into blood (via pertubular capillaries)
    3. Tubular secretion
  • Selective movement of some substances from blood (peritubular capillaries) back into filtrate
33
Q

Three components of filtration membrane

A
  1. Fenestrated endothelial cells of glomerulus
  2. Glomerular basement membrane (GBM)
  3. Podocytes with slit diaphragms
34
Q

What is the composition of the filtrate in the Bowmans Capsular space?

A
  • Similar to plasma only no proteins
35
Q

Why don’t plasma proteins pass into the Bowmans Capsular space under normal circumstances?

A
  • Glomerular filtration membrane pores are too small
36
Q

Glomerular filtration rate (GFR)

A

volume of fluid filtered from the glomeruli into bowmans capsule each minutes
- GFR averages 125mL/min or 180 L/day

37
Q

Three functions of the PCT

A
  1. Reabsorption of organic nutrients
  2. Reabsorption of ions
  3. Reabsorption of water
37
Q

Three functions of the PCT

A
  1. Reabsorption of organic nutrients
  2. Reabsorption of ions
  3. Reabsorption of water
38
Q

Reabsorption at the PCT

A
  • PCT cells normally reabsorb 60-70% of filtrate produced in glomerulus/renal corpuscle
  • Substances for reabsorption diffuse out of tubular into adjacent peritubular blood capillaries
39
Q

What part of the nephron is involved with obligatory water, ion, and organic nutrient reabsorption?

A

PCT

40
Q

Reabsorption along the nephron loop

A
  • Mainly reabsorption of water and NA and CI ions
  • Further reabsorption go water (descending limb)
  • Reabsorption of Na and K and CI ions (ascending limb)
  • Sets up a concentration gradient so water can be reabsorbed and at the same time makes concentrated urine
41
Q

Reabsorption in the DCT

A
  • Hormonally regulated by aldosterone and parathyroid hormone (PTH)
  • Variable reabsorption of water Na and Ca under hormonal control
  • DCT cells reabsorb tubular sodium Na positive (by aldosterone and water follows)
  • DCT cells reabsorb calcium
42
Q

What is Filtrate?

A

blood plasma minus blood proteins and blood cells

43
Q

What is Urine?

A

filtrate minus water, nutrients, essential ions via reabsorption, plus added wastes via secretion

44
Q

Filtration becoming urine process?

A
  • In DCT and collecting ducts final secreted ions combine with the filtrate to become urine
  • Urine then drains into the renal pelvis
  • The urine passes into the ureters
  • Ureters drain into the urinary bladder
  • Urine is held in the urinary bladder until micturition when it is excreted through the urethra and out of body
45
Q

urine composition

A
  • Usually clear, and pale to dark yellow
  • Should be no glucose or amino acids (normal reabsorbed in PCT), also no protein (never filtered at glomerulus)
  • Variations could indicate pathology
  • 95% water
  • 5% solutes (in decreasing order of concentration)
46
Q

The GFR (Glomerular filtration rate) is Regulated by 2 mechanisms that ensure adequate blood flow to kidneys and normal filtration pressures:

A

These 2 mechanisms are
Intrinsic
Extrinsic

47
Q

What is Intrinsic (autoregulation) mechanism

A

• Intrinsic (autoregulation)- acting locally at kidney and involves the nephrons and,

48
Q

What is Extrinsic mechanism?

A

Extrinsic- acting from a distance e.g. autonomic regulation by sympathetic nerves and hormonal regulation initiated by kidneys

49
Q

Renal regulation of GFR

A 
Juxtaglomerular complex (JGC) 
•	One per nephron
•	Important in regulation of rate of filtrate formation and blood pressure
•	Consists of three cell populations:
these three cell populations are 
1.	Extraglomerular mesangial cells
2.	Macula densa
3.  Juxtaglomerular cells
50
Q

Describe the three cell populations of Renal regulation of GFR

A
  1. Extraglomerular mesangial cells
    • Smooth muscle cells. Sense stretch in wall of afferent arteriole due to every-day fluctuations in BP. Important in local intrinsic autoregulation of GFR
  2. Macula densa
    • Chemoreceptors; sense NaCl content of filtrate e.g. decreased NaCl often due to a decrease in GFR. Important in local intrinsic autoregulation of GFR
  3. Juxtaglomerular cells, or JG cells (Granular cells) in walls of afferent arteriole
    • Mechanoreceptors; sense extreme changes in blood pressure in afferent arteriole and synthesise, store & secrete renin. Important in extrinsic regulation.
51
Q

Renal control of Erythropoiesis

A

Erythropoiesis - production of red blood cells
• Stimulated by the hormone erythropoietin (EPO)
• Released by kidneys in response to hypoxia
• Causes of hypoxia include:
• Decreased RBC numbers due to haemorrhage or increased destruction
• Insufficient haemoglobin per RBC (e.g. iron deficiency)
• Reduced availability of O2 (e.g. high altitudes)

Physiology (6 decks)

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