1
Q
what is the main function of the kidney?
A
excretion
2
Q
what does the kidney excrete?
A
metabolic waste:
- urea
- creatinine
- uric acid
- end products of haemoglobin breakdown
- hormone metabolites
foreign substances:
- drugs
- pesticides
- food additives
3
Q
what is urea?
A
breakdown product of amino acids
4
Q
what is creatinine?
A
breakdown product from skeletal muscle
5
Q
what is uric acid?
A
breakdown product of nucleic acids
6
Q
give an example of an end product of haemoglobin breakdown that is excreted by the kidneys
A
bilirubin
7
Q
aside from excretion, give 5 other functions of the kidneys
A
- control of water and electrolyte balance
- control of arterial BP and blood volume
- control of acid-base balance
- endocrine functions
- glucose synthesis (gluconeogenesis)
8
Q
the kidney controls water and electrolyte balance. give 3 examples of ion levels that the kidneys control
A
K+
Na+
Cl-
9
Q
describe and explain how the kidneys control acid-base balance
A
- H+, HCO3- balances
- kidneys work together with lungs and the body’s own buffers to address acid-base balance
10
Q
describe some endocrine substances that the kidneys help to regulate / control
A
EPO
renin
calcitriol
11
Q
what is EPO involved in?
A
RBC production in the bone marrow
12
Q
when do the kidneys help to synthesise glucose by gluconeogenesis?
A
in prolonged fasting
13
Q
what does kidney failure lead to?
A
- disruption of homeostatic functions of the kidneys
- severe abnormalities in body fluid volumes and composition
14
Q
describe the anatomy of the kidney in terms of where it is situated in the body (not its internal structure)
A
- paired bean-shaped organs
- lie in the back of the abdominal cavity and on either side of the vertebral column
- right kidney sits slightly lower due to the large lobe of the liver
15
Q
how does urine travel from the kidney to the outside of the body?
A
- urine leaves kidney and travels via the ureter to the bladder
- it then leaves the bladder to the outside of the body
16
Q
label the image
A
17
Q
describe and explain the internal anatomy of the kidney
A
- kidney is surrounded by tough fibrous renal capsule as well as visceral fat
- fat protects the kidney from mechanical shock (tissue is fragile)
- medial side of kidney contains a ‘notch’ (hilum) from which renal artery, renal vein, nerves, pelvis and ureter pass through
18
Q
what are the cortex, medulla, pyramids and nephrons?
A
- outer ‘grainy’ cortex and an inner medulla
- medulla is divided into multiple cone-shaped regions called pyramids
- nephrons = the functional units of the kidney
19
Q
label the image
A
20
Q
how many nephrons are in each kidney through a person’s lifetime?
A
- each kidney is composed of about 1 million nephrons
- when over 40, every 10 years there is a natural loss of 10% of nephrons
- i.e. at 70, 30% fewer nephrons
21
Q
what sorts of components do the nephrons consist of?
A
vascular components and tubular components
22
Q
describe and explain the blood supply to the kidneys
A
- blood flow to both kidneys is around 20-25% of total cardiac output
- blood circulation in the kidney is unique as it has 2 capillary beds (glomerular and peritubular capillaries)
23
Q
compare the red, blue and yellow vessels in the image
A
- yellow = tubular elements of nephron
- red = oxygenated blood
- blue = deoxygenated blood
24
Q
describe the organisation of the tubular elements of the nephron and how blood moves through them
A
- afferent arterioles deliver blood to the glomerular capillaries
- glomerular capillaries rejoin to form efferent arterioles
- efferent arterioles subdivide inti peritubular capillaries
25
function of afferent arterioles in the nephrons
- deliver blood to glomerular capillaries
- contained within the head of the tubular element (Bowman's capsule)
- filtration occurs, start of urine formation
26
what happens in where glomerular capillaries rejoin to form efferent arterioles?
unfiltered blood leaves the glomerulus
27
what do peritubular capillaries do in the kidney?
supply blood all around the kidney
28
what are the 2 capillary beds in the nephron / kidney?
glomerular and peritubular (around-tubular)
29
label this image
30
label this image
31
where are glomerular capillaries?
encapsulated in the Bowman's capsule
32
simple function of the Bowman's capsule
collects filtered fluid from the capillaries
33
describe ultrafiltration
- first step of urine formation
- solutes get pushed out of capillaries into the inside of the Bowman's capsule
- Bowman's capsule collects filtered fluid and sends it down to the rest of the tubule
34
describe the order of the tubular components of the nephron
Bowman's capsule
PCT
loop of Henle
DCT
CD
35
describe the structure of the tubular components of the nephron
- PCT is convoluted and straightens into LoH
- LoH allows for the dip between the cortex and medulla
- DCT is convoluted again then the contents is emptied into the CD which travels to the pelvis of the kidney
- CD empties into the ureter which then goes to the bladder
36
where is the PCT situated in the nephrons? what is its function?
- continues from Bowman's capsule
- lies entirely in the cortex
- key site of reabsorption
37
describe the structure of the PCT
- composed of single layer of cuboidal cells which interlock tightly and extensively, connected by tight junctions at their luminal surfaces
- microvilli (highly folded lumen-facing membrane)
38
function of the microvilli in the PCT
- increase the membrane surface area facing the inside of the tubule
- allows for reabsorption to take place
39
describe the structure of the LoH
- forms a U-shape (hairpin) that dips into the medulla
composed of:
- thin descending limb
- thin ascending limb
- thick ascending limb
40
structure and location of thin descending limb in LoH
ends in hairpin turn and plunges from the cortex into the medulla
41
are all LOHs the same?
only long loops of Henle have thin ascending limbs
42
key role of LoH
key role in urine concentration
43
describe the structure of the macula densa
- short segment of cells present at the end of the thick ascending limb of the LoH in the DCT
- comes very close to the renal corpuscle and fork between afferent and efferent arterioles
44
what is the juxtaglomerular apparatus and what is it made up of? what is its function?
- macula densa and juxtaglomerular granular cells form the juxtaglomerular apparatus
- plays a very important role in controlling nephron function
45
what are juxtaglomerular granular cells and what is their function?
- they are vascular smooth muscle cells
- they secrete renin
46
label this image of the juxtaglomerular apparatus
47
compare the structure of the DCT against that of the PCT
DCT is shorter and less convoluted than the PCT
48
describe the structures / functions of the DCT and collecting ducts together
- DCT empties into the CD
- each CD may drain from up to 8 separate nephrons
49
what cells are the late DCT and CD made up of?
- principal cells (P cells)
- intercalated cells (I cells)
50
what are intercalated cells in the late DCT and CD for?
acid-base balance
51
where do collecting ducts pass through in the kidney and why?
pass through the cortex and medulla to empty urine into the renal pelvis (ureter to bladder)
52
what receptors are stimulated in the kidneys, what are they stimulated by and where are the receptors located specifically?
both stimulated by sympathetic nervous system (noradrenaline)
- alpha 1 adrenoceptors are on vascular smooth tissue
- beta adrenoceptors are on juxtaglomerular granular cells
53
describe and explain the innervation of the alpha adrenoceptors in the kidney
- activation of alpha 1 adrenoceptors expressed on vascular smooth tissue = vasoconstriction (reduced blood vessel diameter)
- seen greater in afferent arterioles than efferent
- vasoconstriction can decrease blood flow to nephrons and reduce GFR
54
describe and explain the innervation of the beta adrenoceptors in the kidney
- activation of beta adrenoceptors expressed on juxtaglomerular granular cells leads to the release of renin
- renin is part of the RAAs that leads to angiotensin II formation
55
list 4 hormones that act on the kidney
- ADH
- aldosterone
- parathyroid hormone
- natriuretic peptides
56
list 4 hormones produced by the kidney
- EPO
- renin
- vit D3 (calcitriol)
- prostaglandins
57
action of ADH on kidney
- increase permeability to water
- leads to increased water reabsorption (antidiuresis)
- increases permeability of nephron to water
58
action of aldosterone on kidney
- part of RAAS
- increases sodium (and water) reabsorption (= natriuresis and diuresis)
- increases potassium secretion
59
action of parathyroid hormone on the kidney
- involved in plasma calcium homeostasis
- increase calcium ion reabsorption
60
action of natriuretic peptides on the kidney
- natriuresis = increase in Na+ excretion (with accompanying diuresis)
- via inhibition of Na+ reabsorption, suppression of RAAs and vascular effects
vascular effects include vasodilation of afferent arteriole and vasoconstriction of efferent arteriole
61
action of EPO produced by the kidney. what would a lack of this cause?
- stimulate RBC production
- gets haematopoietic stem cells (bone marrow) to differentiate into RBCs
- lack of EPO = lack of RBCs = anaemia
