Chapter 26 - Urinary System Flashcards
1
Q
What are the 8 major functions of the kidneys?
A
- Regulation of blood ionic composition
- Regulation of blood pH
- Regulation of blood volume
- Regulation of blood pressure
- Maintenance of blood osmolarity
- Production of hormones
- Regulation of blood glucose level
- Excretion of wastes and foreign substances
2
Q
Where are the kidneys located?
A
Between the levels of the last thoracic and third lumbar vertebrae
- partially protected by 11th and 12th ribs
3
Q
What is the renal hilum?
A
Indentation near the center of the concave border
- ureter emerges from the kidney along with blood vessels, lymphatic vessels and nerves
4
Q
What are the three layers of the kidney?
A
- Renal capsule
- Adipose capsule
- Renal fascia
5
Q
What is the renal capsule?
What is it’s function?
A
Deepest layer of the kidney
- serves as a barrier against trauma and helps maintain the shape of the kidney
6
Q
What is the adipose capsule?
What is it’s function?
A
Middle layer of the kidney
- protects the kidney from trauma and holds it firmly in place
7
Q
What is the renal fascia?
What is it’s function?
A
Superficial layer of the kidney
- Anchors the kidney to the surrounding structures and to the abdominal wall
8
Q
What are the two distinct regions of the kidneys?
A
- Renal cortex
2. Renal Medulla
9
Q
What is the renal cortex?
A
Superficial region of the kidney
- light red area
10
Q
What is the renal medulla?
A
Inner region of the kidney
- deep, darker, reddish-brown
11
Q
What does the renal medulla consist of?
A
Several cone-shaped renal pyramids
12
Q
What is the renal papilla?
A
The apex (pointy end) of the renal pyramids - points towards the renal hilum
13
Q
What are renal columns?
A
Portions of the renal cortex that extend between renal pyramids
14
Q
What constitutes the parenchyma?
A
The renal cortex and renal pyramids (of the renal medulla)
- it is the functional portion of the kidney
15
Q
What is a nephron?
What does it form?
A
Functional units of the kidneys
- forms filtrate (filtered fluid)
16
Q
What do nephrons drain into?
A
Papillary ducts
- extend through the renal papillae of the pyramids
17
Q
What do the papillary ducts drain into?
A
Minor and major calyces
- cuplike structures
- each kidney has 8-18 minor and 2-3 major
18
Q
Which calyx (major and minor) drains into the other?
A
Minor calyces drain into major calyces
19
Q
From the maor calyces, where does urine drain into?
A
A single large cavity
- renal pelvis
20
Q
How do the kidneys receive blood?
A
Through the renal arteries
21
Q
What is the function of afferent arterioles?
A
Supply the nephrons with blood
- 1 nephron receives 1 afferent arteriole
- carries blood TOWARDS the glomerulus
22
Q
What is the glomerulus?
A
Tangles, ball-shaped capillary network of the kidneys
- afferent arteriole branch into glomerulus
23
Q
What is the function of the efferent arterioles?
A
Form from a convergence of the capillaries of the glomerulus
-carry blood AWAY from the glomerulus
24
Q
What do efferent arterioles divide to form?
A
Peritubular capillaries
- surround tubular parts of the nephron in the renal cortex
25
What are vasa recta?
Long, looped-shaped capillaries extending from some efferent arterioles
- supply tubular portions of the nephron in the renal medulla
- around loop of Henle
26
What is the function of the renal vein?
Carries blood away from the kidneys
| - carries blood to inferior vena cava
27
What is the path of urine drainage?
1. Collecting duct
2. Minor calyx
3. Major calyx
4. Renal pelvis
5. Ureter
6. Urinary bladder
28
What are the two parts of the nephron?
1. Renal corpuscle
| 2. Renal tubule
29
What is the purpose of the renal corpuscle?
Filters blood plasma
| - part of a nephron in the kidney
30
What is the purpose of the renal tubule?
Passes filtered fluid
| - part of a nephron in the kidney
31
What are the two components of the renal corpuscle?
1. Glomerulus (the capillary network)
| 2. Glomerular (Bowman's capsule)
32
What is the glomerular (Bowman's capsule)?
A capsule-shaped membranous structure surrounding the glomerulus of each nephron in the kidneys
- extracts wastes, excess salts, and water from the blood.
33
What does the renal tubule consist of?
1. Proximal convoluted tubule (PCT)
2. Loop of Henle (nephron loop)
3. Distal convoluted tubule (DCT)
34
What do the distal convoluted tubules of several nephrons empty into?
A single collecting duct
35
What do collecting ducts converge and unite into?
Papillary ducts
36
What do papillary ducts drain into?
Minor calyces
37
What is the pathway of fluid flow through a nephron?
1. Glomerular (Bowman's) capsule
2. Proximal convoluted tubule
3. Descending limb of the loop of henle
4. Thin ascending limb of the loop of Henle
5. Thick ascending limb of the loop of Henle
6. Distal convoluted tubule
- -> drains into collecting duct
38
What are cortical nephrons?
- renal corpuscles lie in the outer portion of the renal cortex
- SHORT loops of Henle in the cortex, barely penetrate the renal medulla
39
What are juxtamedullary nephrons?
- renal corpuscles lie deep in the cortex
| - LONG loops of Henle, extend DEEP into the medulla
40
What do nephrons with long loops of Henle enable the kidneys to do?
Excrete very dilute or very concentrated urine
41
In which nephron does the loop of Henele consist of two parts (thick and thin)?
Juxtamedullary nephrons
42
What are podocytes?
Simple squamous epithelial cells of the glomerular capsule
43
What is the capsular (Bowman's) space?
Space between the visceral and parietal layers of the glomerular capsule
- the lumen of the urinary tubule
44
What is the macula densa?
An area of closely packed specialized cells lining the wall of the cortical thick ascending limb
-at the transition to the distal convoluted tubule.
45
What is the function of juxtaglomerular cells (JG)?
| Where are they located?
Helps regulate blood pressure within the kidneys
| - located alongside the macula densa
46
What do principal cells have receptors for?
| Where are principal cells located?
Anti-diuretic hormone (ADH) and aldosterone
| - located in the last part of the distal convoluted tube
47
What is the function of intercalated cells?
Play a role in homeostasis of blood pH
48
In order to produce urine, nephrons and collecting ducts must perform what three basic processes?
1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion
49
What is glomerular filtration?
First step in urine production
- water and most solutes in blood plasma are filtered in glomerular capillaries, move into glomerular capsule and then into renal tubule
50
What happens during tubular reabsorption?
As filtered fluid flows through the renal tubules, 99% is re-absorbed
51
How does re-absorbed water and solutes re-enter the blood?
Through peritubular capillaries and vasa recta
52
What happens during tubular secretion?
As filtered fluid flows through the renal tubules and collecting ducts, materials (wastes, drugs, excess ions) are secreted into the fluid
53
What is the difference between tubular reabsorption and tubular secretion?
```
Reabsorption = returns substances to the bloodstream
Secretion = Removes a substance from the blood
```
54
What is glomerular filtrate?
Fluid that enters the capsular space
55
What forms the leaky barrier known as the filtration membrane?
Golmerular capillaries and the podocytes
- allows passage of water and small solutes
- prevents plasma proteins, blood cells and platelets
56
What are the three filtration barriers?
1. Glomerular endothelial cell
2. Basal Lamina
3. Filtration slit
57
What are fenestrations?
Pores
- allow solutes in blood plasma to exit glomerular capillaries
- prevents filtration of blood cells and platelets
58
What are pedicels?
Foot-like processes that extend from each podocyte
| - wrap around glomerular capillaries
59
What are filtration slits?
Spaces between pedicels
60
What is the slit membrane?
A thin membrane that extends across each filtration slit
- allows only very small things to pass
- water, glucose, vitamins amino acids, urea, ions
61
Why is the volume of fluid filtered by the renal corpuscle larger than other capillaries?
1. Glomerular capillaries have a large surface area
2. Filtration membrane is thin and porous (50x "leakier" than other capillaries)
3. Glomerular capillary blood pressure is HIGH
- efferent arteriole is SMALLER than afferent arteriole
62
Glomerular filtration depends on what three main pressures?
1. Glomerular blood hydrostatic pressure (GBHP)
2. Capsular hydrostatic pressure (CHP)
3. Blood colloid osmotic pressure (BCOP)
63
What is the equation for net filtration pressure (NFP)?
NFP = GBHP - CHP - BCOP
64
What is glomerular blood hydrostatic pressure (GBHP)?
Blood pressure in glomerular capillaries
- approx 55 mmHg
- promotes filtration by forcing water and solutes in blood plasma through the filtration membrane
65
What is the capsular hydrostatic pressure (CHP)?
Hydrostatic pressure exerted against the filtration membrane by fluid already in the capsular space and renal tubule
- OPPOSES filtration
- "back pressure", approx 15 mmHg
66
What is blood colloid osmotic pressure (BCOP)?
Due to the presence of proteins in blood plasma
- OPPOSES filtration
- approx 30 mmHg
67
What is the glomerular filtration rate (GFR)?
Amount of filtrate formed in all the renal corpuscles of both kidneys each minute
68
What are the two WAYS that mechanisms operate to regulate the glomerular filtration rate?
1. Adjusting blood flow into and out of the glomerulus
| 2. Altering the glomerular capillary surface area available for filtration
69
What are the three mechanisms that control GFR?
1. Renal autoregulation
2. Neural regulation
3. Hormonal regulation
70
What is renal autoregulation?
Ability of the kidneys to help maintain constant renal blood flow and GFR
- despite normal changes in blood pressure
71
What are the two mechanisms of renal autoregulation?
1. Myogenic Mechanism
| 2. Tubuloglomerular feedback
72
What is the myogenic mechanism?
Mechanism of renal autoregulation
- occurs when stretching triggers contraction of smooth muscle cells in the walls of afferent arterioles
- as blood pressure rises, GFR rises
- elevated blood pressure stretches afferent arterioles
- in response, smooth muscles contract, decreasing blood flow
73
What is tubuloglomerular feedback?
Mechanism of renal autoregulation
- macula densa provide feedback to the glomerulus
- if GFR is high due to high blood pressure, there is less time to re-absorb Na+ and Cl- and water
- macula densa detect this increased delivery of Na+, Cl- and water
74
What happens to afferent and efferent arterioles with moderate sympathetic stimulation?
They both constrict to the same degree
- blood flow into and out of glomerulus is restricted to the same extent
- decreases GFR only slightly
* * if there is significant sympathetic stimulation, afferent vasoconstriction dominates (GFR drops)
75
What are the two hormones that contribute to the regulation of GFR?
1. Angiotensin II - reduces GFR
| 2. Atrial natriuretic peptide (ANP) - increases GFR
76
How does angiotensin II reduce GFR?
Very potent vasoconstrictor
- narrows both afferent and efferent arterioles
- reduces renal blood flow, decreasing GFR
77
How does atrial natriuretic peptide (ANP) increase GFR?
Causes relaxation of the glomerular mesangial cells
- ANP increases the capillary surface area available for filtration
- GFR rises as capillary surface area rises
78
What are the two important outcomes of tubular secretion?
1. Secretion of H+ helps control blood pH
| 2. Secretion of other substances helps eliminate them from the body
79
What are the two routes that a substance can take being re-absorbed?
1. Can move between adjacent tubule cells
| 2. Through an individual tubule cell
80
What is paracellular reabsorption?
Fluid leaks BETWEEN the cells in a passive process
81
What is transcellular reaborption?
Substances pass from the fluid in the tubular lumen THROUGH the apical membrane of the tubule cell
82
What is primary active transport?
Uses the energy derived from the hydrolysis of ATP to "pump" a substance across a membrane
83
What is secondary active transport?
Energy stored in an ion's electrochemical gradient, drives another substance across a membrane
84
What is the transport maxium (Tm)?
Limit to how much/fast a transporter can move substances across a membrane
85
What is obligatory water reabsorption?
Water that is reabsorbed with solutes
- occurs via osmosis
- occurs in proximal convoluted tubule and descending loop of Henle
86
What is facultative water reabsorption?
Regulated by anti-diuretic hormone and occurs mainly in the collecting ducts
87
Where does the largest amount of reabsorption (water, Na+, K+, solutes, etc) occur?
In the proximal convoluted tubules
88
What facilitates most of the reaborption that happens in the PCT?
Na+!
- Na+ symporter (reabsorb glucose)
- Na+ antiporter (secrete H+)
89
What is NH3?
Ammonia - a poisonous waste product derived from the deamination of various amino acids
90
What is the importance of the PCT with regards to NH3?
PCT can produce additional NH3
- reaction also generates HCO3-
- NH3 binds to extra H+ --> NH4 (ammonium)
91
What happens in the loop of Henle?
Reaborbs even more water, Na+, K+, Cl- and HCO3-
- reabsorption of water is NOT automatically coupled to reabsorption of filtered solutes
- loop is relatively impermeable to WATER
92
How is the descending loop different from the ascending loop of Henle?
```
Descending = water is reabsorbed
Ascending = little to NO water is reaborbed
```
93
What is mainly reabsorbed in the distal convoluted tubules?
Major site where parathyroid hormone (PTH) stimulates reabsorption of Ca2+
94
What are the two kinds of cells present in the DCT, what do they reabsorb, what do they secrete?
Principal cells - reabsorb Na+, secrete K+
| Intercalated cells - reabsorb K+ AND HCO3- , secrete H+
95
What are the five hormones that affect the extent of Na+, Cl-, Ca2+ and water reaborption as well as K+ secretion in renal tubules?
1. Angiotensin II
2. Aldosterone
3. Anti-diuretic hormone
4. Atrial natriuretic peptide
5. Parathyroid hormone
96
What are the three main ways that angiotensin II affects renal physiology?
1. Decreases the GFR by causing vasoconstriction of the afferent arterioles
2. Enhances reaborption of Na+, Cl- and water in the PCT by stimulating the activity of the Na+/H+ antiporters
3. Stimulates the adrenal cortex to release aldosterone (stimulates principal cells to reabsorb more Na+ and Cl- and secrete more K+)
- increases in blood volume and blood pressure
97
What is renin?
Enzyme secreted by and stored in the kidneys that promotes the production of the protein angiotensin
98
What is angiotensin II?
Hormone that causes vasoconstriction and a subsequent increase in blood pressure
99
What is the function of aldosterone?
Hormone that stimulates absorption of sodium by the kidneys and so regulates water and salt balance
100
What is the function of the anti-diuretic hormone (ADH) (vasopressin)?
Hormone that acts to promote the retention of water by the kidneys and increase blood pressure
101
What is the function of the atrial natriuretic peptide (ANP)?
Able to inhibit reabsorption of Na+ and water in the PCT and collecting ducts
- suppresses secretion of aldosterone and ADH
102
What hormone controls if urine produced is dilute or concentrated?
ADH
- in the absence of ADH, urine is very dilute
- high levels of ADH, urine is very concentrated
103
How is dilute urine formed?
Osmolarity of the fluid in the tubular lumen INCREASES as it flows down the descending limb of the loop
- osmolarity DECREASES as it flows up the loop
- osmolarity DECREASES MORE as it flows through the rest of the nephron
104
What does the formation of concentrated urine depend on?
Presence of an osmotic gradient
105
What are the two main factors that contribute to creating the osmotic gradient?
1. Differences in solute and water permeability and reabsorption in different sections of the LONG loops of Henle
2. Countercurrent flow of fluid through tube-shaped structures in the renal medulla
106
What is countercurrent flow?
Refers to the flow of fluid in opposite directions
107
What are the steps in creating concentrated urine?
1. Symporters in thick ascending limb cells of loop of Henle cause a buildup of Na+ and Cl- in the renal medulla
2. Countercurrent flow through the loop establishes an osmotic gradient in the renal medulla
3. Principal cells in collecting duct reabsorb more water when ADH is present
4. Urea recycling causes buildup of urea in renal medulla
108
What is urinalysis?
Analysis of the volume, and physical, chemical and microscopic properties of urine
109
What are the two blood tests that can give an indication as to kidney function?
1. Blood urea nitrogen (BUN) test - measures blood nitrogen levels
2. Plasma creatinine
110
What is renal plasma clearance?
The volume of blood that is "cleaned" or cleared of a substance per unit of time
- high renal clearance indicates efficient excretion
- low renal clearance indicates inefficient excretion
111
What is the flow of urine from the minor calyces?
Major calyces --> renal pelvis --> ureters --> urinary bladder --> urethra
112
What is the function of the ureters?
Transports urine from the renal pelvis of the kidneys to the urinary bladder
113
How is urine passed through the ureters?
By peristaltic contractions of the muscular walls of the ureters
- hydrostatic pressure and gravity also help
114
What prevents backflow of urine from the urinary bladder into the ureters?
As the urinary bladder fills, pressure within it compresses the oblique openings into the ureters and prevents backflow
115
What is the urinary bladder?
A hollow, distensible muscular organ in the pelvic cavity
- holds urine
- 700-800 mL, but smaller in females
116
What is the trigone?
Small triangular area in the floor of the urinary bladder
| - contains the two ureteral openings
117
What is the internal urethral orifice?
The opening into the urethra
118
What are the three walls of the urinary bladder made of?
1. Mucosa - deepest
2. Muscularis - intermediate
3. Adventitia - superficial
119
What is the detrusor muscle?
Also called the muscularis layer of the bladder
- consists of three layers of smooth muscle fibers:
1. Inner longitudinal
2. Middle circular
3. Outer longitudinal
120
What do the circular fibers around the opening to the urethra form?
Internal urethral sphincter (involuntary)
121
What is the external urethral sphincter composed of?
Composed of skeletal muscles (VOLUNTARY)
122
What is the micturition?
Discharge of urine from the urinary bladder
123
Where is the micturition center?
In sacral spinal cord segments S2 and S3
124
What is the micturiton reflex?
Stretch receptors transmit nerve impulses to the micturition center
- cause the contraction of the detrusor muscle and relaxation of the internal urethral sphincter muscle
125
What is the urethra?
Small tube leading from the internal urethral orifice to the exterior of the body
126
What is the external urethral orifice?
Opening of the urethra to the exterior
127
Where is the female external urethral orifice located?
Between the clitoris and the vagina
128
How is the male urethra divided (3 parts)?
1. Prostatic urethra - passes through the prostate
2. Membranous (intermediate) urethra - passes through deep muscles of perineum
3. Spongy urethra - longest portion, passes through the penis
129
What are renal calculi or kidney stones?
Crystals of salts present in urine occasionally precipitate and solidify into insoluble stones
- if they get stuck, they are very painful
130
What is a urinary tract infection (UTI)?
Infection of a part of the urinary system or the presence of large numbers of microbes in the urine
- drink cranberry juice!
131
What are glomerular diseases?
The filtration membrane sustains damage, permeability increases
132
What is renal failure?
A decrease or cessation of glomerular filtration
- acute renal failure (abruptly stops working)
- chronic renal failure (gradually stops working)
133
What is polycystic kidney disease (PKD)?
Inherited disorder
- kidney tubules become riddled with hundreds or thousands of cysts
- results in end-stage renal failure
134
What is enuresis?
Involuntary voiding of urine after the age at which voluntary control has typically been attained
135
What is intravenous pyelogram (IVP)?
X-ray of the kidneys, ureters, urinary bladder after venous injection of a radiopaque contrast medium
136
What is polyuria?
Excessive urinary formation
| - occurs in diabetes mellitus and glomerulonephritis
137
What is urinary retention?
Failure to completely or normally void urine
