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Year 2: Human Anatomy and Physiology > RS: Renal System > Flashcards

RS: Renal System Flashcards

1
Q

What are the principle organs of the renal system?

A

The kidneys

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2
Q

What are the accessory organs of the renal system?

A

Ureters, bladder and urethra

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3
Q

Where are the kidneys positioned?

A

The kidneys are positioned, retroperitoneal, to the T12 and L3 components of the spinal cord.
The right kidney tends to be lower and smaller than the left kidney, and the adrenal glands are positioned above both kidneys.

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4
Q

What are the primary functions of the renal system?

A
  1. Excretion- endogenous and exogenous waste, and drugs and their metabolites
  2. Osmoregulation- water and electrolyte balance
  3. Acid base balance
  4. Endocrine— production of hormones
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5
Q

What are the 2 regions of the kidney?

A

The outer cortex and the inner medulla

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6
Q

Describe the structure of the cortex and medulla of the kidneys

A

he outer cortex consists of a fibrous outer capsule. The inner medulla is composed of 8-15 triangular pyramids, containing nephrons, that apex at the renal papilla to drain into the collecting ducts, then via papillary ducts, into the minor calyx then major calyx. Major calyces lead to the pelvis and then eventually the ureters, before eventually entering the urinary bladder.

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7
Q

How does urine exit the body?

A

Urine exits the body via the urethra.

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8
Q

What are the 2 types of nephrons?

A
  1. Cortisol nephron

2. Juxtamedullary nephron

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9
Q

Describe the structure of the cortical ephrons

A

Cortisol nephrons have a short LoH that only just extends into the medulla of the kidneys; mainly reside in the cortisol region of the kidney. Pertibular capillaries surround the nephron to reabsorb nutrients and water back into the blood.

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10
Q

Describe the structure of the juxtamedullary nephrons

A

Glomeruli are at the boundary of the cortex and the medulla, and the long LoH extends into the medulla. Vasa recta, specialised pertibular capillaries, surround the nephrons to reabsorb water and nutrients back into the blood.

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11
Q

What is the function of the proximal convoluted tubule?

A

Responsible for reabsorbtion and some excretion

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12
Q

What is the type of epithelia in the proximal convoluted tubule?

A

Simple cuboidal epithelium with microvilli

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13
Q

What is the function of the thin descending limb of the LoH?

A

Responsible for reabsorbtion

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14
Q

What is the type of epithelia in the thin descending limb of the LoH?

A

Simple squamous epithelium

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15
Q

What is the type of epithelia in the thick ascending limb of the LoH?

A

Simple cuboidal epithelium with no microvilli

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16
Q

What is the function of the thick ascending limb of the LoH?

A

Responsible for reabsorbtion

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17
Q

What is the function of the distal convoluted tubule?

A

Responsible for secretion and some reabsorption

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18
Q

What is the type of epithelia in the distal convoluted tubule?

A

Simple cuboidal epithelium with few microvilli

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19
Q

How much filtrate do the kidneys produce each day before reabsorption?

A

180L

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20
Q

How much of the filtrate is reabsorbed by the kidneys?

A

99.9%

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21
Q

What do the kidneys filter out of the blood?

A

The kidneys filter water and small, dissolved solutes (eg. Salts, glucose, amino acids, metabolic waste), but not proteins or blood cells. What can be filtered by the kidneys is related to size and charge; small, positively charged molecules can be filtered more easily than negatively charged ion.

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22
Q

What can be filtered more easily: positive ions or negative ions?

A

Small, positively charged molecules can be filtered more easily than negatively charged ions.

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23
Q

What regions of the kidney nephron carries out the majority of obligate reabsorption?

A

The proximal convoluted tubule

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24
Q

Describes the process of reabsorption in the proximal convoluted tubule

A

Sodium ion active transport drives the passive reabsorption of chloride and phosphate ions. Ion transport drives obligatory water reabsorption by osmosis via aquaporins. All glucose and nutrients, and some urea, is reabsorbed.

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25
Q

Where else can reabsorption take place?

A

In the distal convoluted tubule

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26
Q

What type of reabsorption takes place in the distal convoluted tubule?

A

Facultative reabsorption of anything that is needed back in the blood

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27
Q

What type of reabsorption takes place in the proximal convoluted tubules?

A

Obligate reabsorption

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28
Q

What is secretion in the kidneys?

A

Active and passive transport of substances from the peritubular blood into the filtrate. Potassium ions, hydrogen ion, urea, ammonium ions, and some drugs such as penicillin, are secreted into into the nephron from the filtrate, usually at the distal convoluted tubule.

29
Q

Where does secretion usually occur?

A

In the distal convoluted tubule

30
Q

Where does filtration take place?

A

At the glomerulus, contained within the Bowman’s capsule

31
Q

What adaptation of the kidneys make it adapted for its role in filtration?

A

Highly vascularised to allow efficient exchange of materials from the blood to the kidneys for filtration

32
Q

Describe the movement of blood through the kidneys

A

Blood entering the kidneys enters the renal artery which splits into segmental arteries . The blood moves through the renal columns which are between the renal pyramids. Filtered blood leaving the kidneys leaves via the renal vein, which has a similar branched network to the renal artery.

33
Q

How do the nephrons regulate excretion of materials from the body?

A
  1. Filtration
  2. Reabsorption
  3. Secretion
34
Q

What is the calculation to determine excretion rate?

A

Excretion rate = filtration rate - reabsorption rate + secretion rate

35
Q

What is the GFR?

A

Volume of filtrate produced per a minute

36
Q

What is the calculation for GFR?

A

GFR= glomerular hydrostatic Pressure - (Bowman’s capsule pressure + glomerular osmotic pressure)

37
Q

What adaptation makes the glomerulus and Bowman’s capsule adapted to their role of filtration?

A

Surrounded by a capillary network from efficient diffusion of blood content into the kidney nephrons, to form the filtrate.

38
Q

Describe the structure of the glomerulus

A

The glomerulus consists of a single endothelial cell layer with fenestrations (pores) that provide increased porosity for filtration to occur; easier movement of filtrate.

39
Q

What are the vessels that carry blood into and out of the glomerulus?

A

Vessels leading into the glomerulus are called afferent arterioles and vessels leaving the glomerulus are called efferent (EXIT) arterioles.

40
Q

Describe the structure of the Bowman’s capsule

A

The Bowman’s capsule consists for a double layer of epithelial cells with a capsular space in between. Fluid, waste and electrolytes pass through glomerular capillaries, across the Bowman’s capsule, to form filtrate. The outer parietal wall consists of simple squamous epithelium, whereas the inner visceral wall consists of specialised cells called podocytes (cells with feet).

41
Q

What are the 3 layers of the glomerular capsular filtration membrane?

A
  1. Glomerular capillary endothelium
  2. Glomerulus basement membrane
  3. Podocyte cells of the Bowman’s capsule
42
Q

Describe the capillary endothelium

A

Contains fenestrations (pores) th make the renal capillaries more permeable to water-soluble solutes and act as a screen to stop blood cells and large proteins leaving

43
Q

Describe the glomerular basement menu

A

A filamentous layer that consists of collagen fibres embedded in a proteoglycan matrix that is negatively charged to prevent plasma proteins filtration

44
Q

Describe the visceral podocyte layer of the Bowman’s capsule

A

Visceral podocyte cells have processes (trabecular) that extend and produce fenestration slit pores to allow selective filtration; negative charge also prevents protein filtration. Podocytes are also responsible for maintaining the basement membrane and for phagocytising molecules such as albumin that have escaped.

45
Q

How much urine is produced each day?

A

Roughly 1.5L

46
Q

What is the minimum amount of urine that needs to be produced to excrete all waste materials from the body?

A

500ml

47
Q

What is the principle componentnof urine?

A

Water

48
Q

What are the components of urine?

A

Water, urea, chloride, sodium, potassium and creatinine

49
Q

What are mesangial cells?

A

Measngial cells are found in the centre of the glomerular capillary network and are responsible for secreting ECM to support glomerular structure, phagocytic activity and prevent the accumulation of macromolecules. Cells are capable of involuntary contraction to change their filtration surface are; alters GFR.

50
Q

What are the primary functions of the kidneys/ renal system?

A
  1. Excretion
  2. Osmoregulation
  3. Endocrine
  4. Acid-base balance
51
Q

How do the kidneys facilitate excretion?

A

Excretion of endogenous waste products such as excess water, electrolytes (chloride, sodium, potassium, and bicarbonate ions). Excretion of nitrogen containing metabolites such as urea, creative (muscle) and URAC acids (nucleic acids); surplus phosphate; surplus sulphate; and steroid hormones following hepatic transformation to a more hydrophilic state eg, progesterone and testosterone.

Excretion of exogenous waste products such as water soluble drugs and lipid soluble drugs (following hepatic transformation to a more hydrophilic form).

52
Q

How do the kidneys facilitate osmoregulation?

A

Maintenance of water and electrolyte balance to keep osmotic pressure of bodily fluids constant and to maintain blood pressure. Reabsorption of sodium ions and water, in exchange for potassium ions, to regulate blood pressure.

53
Q

What are the 3 hormones produced by the kidneys?

A
  1. Erythropoietin (EP)
  2. Renin
  3. 1,25- Dihydroxycalciferol (active vitamin D)
54
Q

What is the role of Erythropoietin?

A

Erythropoietin is the glycoprotein responsible for the increase in RBC production by the bone marrow in response to hypoxia (low oxygen levels) to increase uptake of oxygen.

55
Q

What is the role of renin?

A

Renin is released by the juxtamedullary cells of the kidney nephrons to activate angiotensin I production from angiotensinogen. Angiotensin I is then converted to angiotensin II by ACE, to trigger the the uptake and reabsorption of sodium ions and water, in exchange for potassium ions, to restore blood pressure. Angiotensin II activates aldosterone production by the adrenal glands.

56
Q

What is the role of 1,25- Dihydroxycalciferol?

A

Hydroxylation of 25-hydroxycalciferol (from the liver) to active vitamin D in the kidneys, which increases calcium and phosphate absorption from the gut and the diet. Vitamin D is needed for the facilitated diffusion of calcium across the enterocytes (cells of the SI) into the blood.

57
Q

How do the kidneys facilitate acid-base balance?

A

The kidneys control blood bicarbonate levels to replace bicarbonate lost during buffering of metabolic acids (eg. Lactic acid).

58
Q

What is osmoregulation?

A

Osmoregulation is the maintenance of constant osmotic pressure through control of water and electrolyte balance

59
Q

What are electrolytes?

A

An electrolyte dissociates in water to form ions (electrically charged atoms).

60
Q

How is water lost from the body?

A

Water is lost from the body via the skin (direct and indirect perspiration), lungs, faeces, and the urine.

61
Q

What is the primary physiological mechanism controlling volume of water excreted by the kidneys?

A

ADH hormonal secretion

62
Q

Describe the action of ADH

A

ADH binds to receptors of the basolateral membrane of the collecting ducts and stimulates, via cAMP, the migration and fusion of vesicles containing aquaporins with the apical luminal membrane.

63
Q

What is osmosis?

A

Osmosis is the movement of water across a partially permeable membrane, due a water potential (osmotic) gradient.

64
Q

What is molarity?

A

Molarity describes the number of moles of the substance per liter of liquid. Molarity is a concentration unit, defined to be the number of moles of solute divided by the number of liters of solution.
Since the volume of solution changes with the amount of solute added as well as with changes in temperature and pressure, osmolarity is difficult to determine

65
Q

What is molality?

A

Molality, also called molal concentration, is a measure of the concentration of a solute in a solution in terms of amount of substance in a specified amount of mass of the solvent. This contrasts with the definition of molarity which is based on a specified volume of solution.
Since the amount of solvent will remain constant regardless of changes in temperature and pressure, osmolality is easier to evaluate and is more commonly used, and often preferred, in practical osmometry.

66
Q

What are the units of osmolarity and osmolality?

A

Molarity M –
mol.L-1moles of solute per L of solution
Molality m – mol.kg-1moles of solute per Kg of solvent

67
Q

What is the normal plasma osmolarity? What happens when this changes?

A

Normal plasma osmolarlity is around 300 mosmol kg-1. A variation of about ±3 mosmol kg-1 of body water activates osmoreceptors located in the anterior hypothalamus:
•supraoptic nucleus (5/6)
•paraventricular nucleus (1/6)

68
Q

What do the supraoptic and paraventricular nuclei do?

A

Synthesise ADH and axonally transport it to the posterior pituitary for storage in nerve ending secretory granules. ADH increases kidney sodium ion and water reabsorption and the hypothalamic lateral prop tic nucleus osmoreceptors activate the thirst centre to cause the individual to consume more fluids; leads to decrease in osmolality and negative feedback loop.

Year 2: Human Anatomy and Physiology (18 decks)

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