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A&P 2 > Lesson 18-19 > Flashcards

Lesson 18-19 Flashcards

1
Q

what are the six principal organs of the urinary system

A
  • two kidneys
  • two ureters
  • urinary bladder
  • urethra
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2
Q

what are the functions of the kidneys (7)

A
  • filter blood and excrete toxic metabolic wastes
  • regulate volume, pressure, and osmolarity
  • regulate electrolytes and acid-base balance
  • secrete erythropoietin
  • help regulate calcium levels
  • clear hormones from blood
  • detoxify radicals
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3
Q

the kidneys secrete erythropoietin. what does that do?

A

stimulates the production of red blood cells

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4
Q

how do the kidneys regulate calcium levels?

A

participating in calcitriol synthesis

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5
Q

what do the kidneys do in starvation?

A

synthesize glucose from amino acids

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6
Q

waste

A

any substance that is useless to the body or present in excess of the body’s needs

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7
Q

metabolic waste

A

waste substance produced by the body

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8
Q

what type of metabolic waste is most toxic to the body?

A

nitrogenous waste

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9
Q

urea

A
  • from protein catabolism
  • breakdown of macromolecules
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10
Q

what is the normal concentration of blood urea?

A

10-20 mg/dL

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11
Q

uric acid

A

product of nucleic acid catabolism

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12
Q

creatinine

A

product of creatine phosphate catabolism

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13
Q

blood urea nitrogen (BUN)

A

level of nitrogenous waste in blood

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14
Q

azotemia

A
  • elevated BUN
  • may indicate renal insufficiency
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15
Q

azotemia may progress to _____

A

uremia

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16
Q

uremia

A

syndrome of diarrhea, vomiting, dyspnea, and cardiac arrhythmia stemming from the toxicity of nitrogenous waste

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17
Q

excretion

A

separating wastes from body fluids and eliminating them

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18
Q

what are the four body systems that carry out excretion

A
  • respiratory
  • integumentary
  • digestive
  • urinary
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19
Q

what does the respiratory system excrete? (3)

A
  • CO2
  • small amounts of other gases
  • water
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20
Q

what does the integumentary system excrete? (4)

A
  • water
  • inorganic salts
  • lactate
  • urea in sweat
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21
Q

what does the digestive system excrete? (7)

A
  • water
  • salts
  • CO2
  • lipids
  • bile pigments
  • cholesterol
  • other metabolic wastes
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22
Q

what does the urinary system excrete? (7)

A
  • many metabolic wastes
  • toxins
  • drugs
  • hormones
  • salts
  • H+
  • water
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23
Q

How much does each kidney weigh?

A

150g

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24
Q

describe the surface structures of the kidneys

A

lateral surface is convex and medial is concave with a slit called the hilum

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25
Q

the hilum of the kidneys receives… (4)

A
  • renal nerves
  • blood vessels
  • lymphatics
  • ureter
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26
Q

describe the kidney position

A
  • lie against posterior abdominal wall of T12 or L3
  • retroperitoneal along with ureters, urinary bladder, renal artery and vein, and adrenal glands
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27
Q

why is the right kidney lower than the left?

A

the large right lobe of the liver

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28
Q

what are the three connective tissue coverings on the kidneys?

A
  • renal fascia
  • perirenal fat capsule
  • fibrous capsule
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29
Q

renal fascia

A
  • immediately deep to parietal peritoneum
  • binds kidney to abdominal wall
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30
Q

perirenal fat capsule

A

cushions kidney and holds it into place

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31
Q

fibrous capsule

A
  • encloses kidney protecting it from trauma and infection
  • collagen fibers extend from fibrous capsule to renal fascia
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32
Q

renal parenchyma

A

glandular tissue that forms urine

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33
Q

renal sinus

A

medial cavity that contains blood and lymphatic vessels, nerves, and urine-collecting structures

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34
Q

what are the two zones of renal parenchyma?

A
  • outer renal cortex
  • inner renal medulla
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35
Q

what is the boundary between the renal cortex and medulla

A

corticomedullary junction

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36
Q

renal columns

A

extensions of the cortex that project inward toward sinus

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37
Q

renal pyramids

A
  • triangular-shaped structures in the renal medulla
  • base adjacent to the cortex while the apex of the pyramid projects into the renal sinus
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38
Q

lobe of kidney

A

one pyramid and its overlaying cortex separated by other lobes of the kidney by the renal column

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39
Q

urine produced in the renal parenchyma is drained by a series of structures. what are they in order? (4)

A
  • minor calyx
  • major calyx
  • renal pelvis
  • ureter
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40
Q

minor calyx

A
  • little cup that surrounds the papilla of each pyramid
  • collects its urine
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41
Q

major calyx

A

formed by convergence of 2 or 3 minor calyces

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42
Q

renal pelvis

A

formed by convergence of 2 or 3 major calyces

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43
Q

ureter

A

tubular continuation of the renal pelvis that drains down to the urinary bladder

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44
Q

each kidney has about ___ nephrons

A

1.2 million

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45
Q

what are the two principal parts of the nephron?

A
  • renal corpuscle
  • renal tubule
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46
Q

renal corpuscle

A

filters the blood plasma

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47
Q

renal tubule

A
  • long coiled tube that converts the filtrate into urine
  • duct leading away from the glomerular capsule and ending at the tip of the medullary pyramid
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48
Q

the renal tubule consists of…(4)

A
  • proximal convoluted tubule (PCT)
  • loop of henle (nephron loop)
  • distal convoluted tubule (DCT)
  • collecting duct (CD)
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49
Q

the renal corpuscle consists of… (2)

A
  • glomerulus
  • two layers glomerular capsule
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50
Q

glomerular capsule

A
  • encloses glomerulus
  • parietal and visceral layers
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51
Q

parietal layer of the glomerular capsule

A
  • outer layer
  • simple squamous epithelium
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52
Q

visceral layer of the glomerular capsule

A
  • inner layer
  • consists of podocytes
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53
Q

podocytes in the visceral layer of the glomerular capsule

A

wrap around capillaries of the glomerulus

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54
Q

the capillaries in the visceral layer of the glomerular capsule are formed by what?

A

afferent arteriole

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55
Q

capsular space

A

separates the two layers of the glomerular capsule

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56
Q

mesangial cells

A
  • pack the spaces among the glomerular capillaries
  • regulate blood flow and phagocytize debris
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57
Q

proximal convolutes tubule

A
  • arises from glomerular capsule
  • longest and most coiled region
  • simple cuboidal epithelium with prominent microvilli
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58
Q

where does the majority of absorption occur in the kidney?

A

proximal convoluted tubule

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59
Q

nephron loop (loop of henle)

A
  • u-shaped portion of renal tubule with a descending and ascending limb
  • thick and thin segment
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60
Q

descending limb of the loop of henle function

A

water reabsorption

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61
Q

ascending limb of loop of henle function

A

sodium and chlorine reabsorption

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62
Q

thick segments of the loop of henle

A
  • simple cuboidal epithelium
  • initial part of descending limb and part or all of the ascending limb
  • nonpermeable to water
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63
Q

describe the thick segments of the loop of henle (2)

A
  • heavily engaged in the active transport of salts and have many mitochondria
  • pump salt and chloride out of tubular fluid
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64
Q

thin segments of the loop of henle

A
  • simple squamous epithelium
  • forms lower part of descending limb
  • very permeable to water
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65
Q

distal convolutes tubule

A
  • begins shortly after the ascending limb re-enters the cortex
  • shorter and less coiled
  • cuboidal epithelium within microvilli
  • end of the nephron
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66
Q

collecting duct

A

receives fluid from the DCTs of several nephrons as it passes back into the medulla

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67
Q

numerous collecting ducts converge towards where?

A

the top of the medullary pyramid

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68
Q

papillary duct

A

formed by merger of several collecting ducts

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69
Q

how many papillary ducts end in the tip of each papilla

A

30

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70
Q

flow of fluid from the point where glomerular filtrate is formed to the point where urine leaves the body (12)

A
  • glomerular capsule
  • proximal convoluted tubule
  • nephron loop
  • distal convolutes tubule
  • collecting duct
  • papillary duct
  • minor calyx
  • major calyx
  • renal pelvis
  • ureter
  • urinary bladder
  • urethra
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71
Q

what are the two types of nephrons

A
  • juxtamedullary nephrons
  • cortical nephrons
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72
Q

juxtamedullary nephrons

A
  • close to medulla
  • very long nephron loops extend as far as apex of renal pyramid
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73
Q

what is the function of juxtamedullary nephrons

A

responsible for maintaining osmotic gradient in the medulla used to help conserve water and concentrate urine

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74
Q

about how many nephrons are juxtamedullary?

A

15%

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75
Q

cortical nephrons

A
  • short nephron loops that dip a short way into medulla
  • some have no nephron loop at all
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76
Q

about what percentage of nephrons are cortical nephrons

A

85%

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77
Q

renal plexus (3)

A
  • nerve and ganglia wrapped around each renal artery
  • issues nerve fibers to blood vessels and convoluted tubules of nephron
  • carries sympathetic innervation from the abdominal aortic plexus
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78
Q

what does sympathetic stim do to the nephron

A

reduces glomerular blood flow and rate of urine production

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79
Q

when is there sympathetic stimulation to the nephron? what happens in this response?

A
  • respond to falling BP
  • stim kidney to secrete renin
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80
Q

renin

A

an enzyme that activates hormonal mechanisms to restore BP to trigger renin-angiotensin system

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81
Q

what are the four stages of urine formation?

A
  • glomerular filtration
  • tubular reabsorption
  • tubular secretion
  • water conservation
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82
Q

what are the three different names given to fluid as it passes through the nephron?

A
  • glomerular filtrate
  • tubular fluid
  • urine
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83
Q

glomerular filtrate

A
  • fluid in the capsular space of the glomerulus
  • similar to blood plasma except that it has almost no proteins
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84
Q

why does glomerular filtrate have little to no proteins?

A

proteins are too big to be filtered into capsular space

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85
Q

tubular fluid

A
  • fluid form the PCT through the DCT
  • substances have been removed or added by tubular cells
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86
Q

urine

A
  • fluid within the collecting duct and beyond
  • undergoes little alteration beyond this point except for changes in water content
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87
Q

glomerular filtration

A

water and some solutes pass from blood within glomerulus into the capsular space of the nephron

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88
Q

filtration membrane

A

barrier through which filtered fluid passes

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89
Q

what are the three components of the filtration membrane used in glomerular filtration

A
  • fenestrated endothelium of the capillary
  • basement membrane
  • filtration slits
90
Q

fenestrated endothelium of the capillary in the filtration membrane

A
  • contains large filtration pores
  • highly permeable but small enough to exclude blood cells
91
Q

what is the size of the filtration pores of the fenestrated endothelium of the capillary

A

70-90 nm

92
Q

basement membrane of the filtration membrane used in glomerular filtration

A
  • proteoglycan gel with negative charge
  • excludes molecules greater than 8 nm
  • smaller albumin repelled by negative charge
93
Q

filtration slits of the filtration membrane used in glomerular filtration

A
  • podocyte foot processes called pedicels wrap around the capillaries
  • have negatively charged filtration slits between them
94
Q

almost any molecule smaller than ___ can pass freely through the filtration membrane

A

3 nm

95
Q

what can pass freely through the filtration membrane (7)

A
  • water
  • electrolytes
  • glucose
  • fatty acids
  • amino acids
  • nitrogenous wastes
  • vitamins
96
Q

what occurs in some substances that makes it to where they cant get through the filtration membrane

A

low molecular weight substances are bound to plasma proteins

97
Q

what are the low molecular weight substances that can be bound to the plasma proteins so that they cant get through the filtration membrane?

A
  • calcium
  • iron
  • through hormone
98
Q

what two things can cause proteins and blood cells to filter through the filtration membrane?

A
  • kidney infections
  • trauma to the filtration membrane
99
Q

proteinuria

A
  • albuminuria
  • albumin in urine
100
Q

hematuria

A

blood in urine

101
Q

glomerular filtration depends on what? (4)

A
  • blood hydrostatic pressure
  • hydrostatic pressure in capsular space
  • colloid osmotic pressure of blood
  • net filtration pressure
102
Q

why is blood hydrostatic pressure higher in the afferent arteriole than the efferent when controlling glomerular filtration

A

afferent arteriole is larger than efferent arteriole

103
Q

what is the standard blood hydrostatic pressure in glomerular filtration

A

60 mmHg

104
Q

hydrostatic pressure in capsular space is due to what?

A

high filtration rate and accumulation of fluid in the capsule

105
Q

what is the standard hydrostatic pressure in the capsular space during glomerular filtration

A

18 mmHg

106
Q

what is the standard colloid osmotic pressure of blood during glomerular filtration

A

32 mmHg

107
Q

why does filtrate have no significant ICOP?

A

because it is almost protein-free

108
Q

what is the standard net filtration pressure

A

10 mmHg

109
Q

what is the direction of fluid travel when it comes to net filtration pressure

A

outward from capillaries to capsular space

110
Q

glomerular filtration rate

A

amount of filtrate formed per minute by the two kidneys combined

111
Q

what is the GFR per minute in a normal male? per day?

A
  • 125 ml/min
  • 180 L/day
112
Q

what is the GFR per minute of a normal female? per day?

A
  • 105 ml/min
  • 150 L/day
113
Q

what does the filtration coefficient (Kf) depend on?

A

permeability and surface area of filtration barrier

114
Q

about how much filtrate is reabsorbed?

A

99%

115
Q

why is 99% of filtrate reabsorbed?

A

only 1-2 L of urine is excreted per day

116
Q

if GFR is too high what happens? (2)

A
  • fluid flows through renal tubules too rapidly for them to reabsorb the usual amount of water and solutes
  • urine output rises increasing chance of dehydration and electrolyte depletion
117
Q

if GFR is too low what happens?

A

wastes are reabsorbed and azotemia may occur

118
Q

what is the only way to adjust GFR?

A

adjust glomerular blood pressure

119
Q

what are the three mechanisms that change glomerular blood pressure

A
  • renal autoregulation
  • sympathetic control
  • hormonal control
120
Q

renal autoregulation

A

the ability of the nephrons to adjust their own blood flow and GFR without external control

121
Q

renal autoregulation enables the kidneys to do what?

A

to maintain a relatively stable GFR in spite of changes in arterial BP

122
Q

what are the two mechanisms of renal autoregulation

A
  • myogenic mechanism
  • tubuloglomerular feedback
123
Q

myogenic mechanism as renal autoregulation

A

if arterial BP increases afferent arteriole is stretched which leads to afferent arteriole constriction which reduces blood flow into the glomerulus

124
Q

tubuloglomerular feedback as renal autoregulation (2)

A
  • when GFR is high macula densa secretes ATP which ultimately stims nearby granular cells to constrict afferent arterioles to reduce GFR
  • granular cells secrete renin if BP is low to trigger the renin-angiotensin-aldosterone system
125
Q

tubuloglomerular feedback involves what?

A

juxtaglomerular apparatus

126
Q

the juxtaglomerular apparatus consists of what two structures?

A
  • macula densa
  • granular/juxtaglomerular cells
127
Q

what kind of nerve fibers richly innervate the renal blood vessels?

A

sympathetic nerve fibers

128
Q

what two things constrict the afferent arterioles

A
  • sympathetic nervous system
  • adrenal epinephrine
129
Q

when does the sympathetic nervous system and adrenal epinephrine constrict the afferent arterioles

A
  • strenuous exercise
  • acute conditions like circulatory shock
130
Q

what is the effect of sympathetic control on the renal system?

A
  • reduces GFR and urine output
  • redirects blood from the kidneys to the heart, brain, and skeletal muscles
  • GFR may be as low as a few millimeters per minute
131
Q

the renin-angiotensin-aldosterone mechanism

A

system of hormones that controls blood pressure and GFR

132
Q

what is the mechanism of the renin-angiotensin-aldosterone mechanism (5)

A
  • when there is a drop in BP baroreceptors in carotid and aorta stim the sympathetic nervous system
  • sympathetic fibers trigger release of renin by kidneys’ granular cells
  • renin converts angiotensinogen to angiotensin 1
  • lungs and kidneys have angiotensin-converting enzyme that converts angiotensin 1 to angiotensin 2
    -BP/fluid volume is restored
133
Q

effects of angiotensin 2 (6)

A
  • raise BP throughout body
  • constrict efferent arterioles in kidneys raising GFR despite low BP
  • stims adrenal cortex to secrete aldosterone which promotes NA and H2O reabsorption in the DCT and collecting duct
  • directly stims Na and H2O reabsorption in PCT
  • stims posterior pituitary to secrete ADH
  • stims thirst and encourages water intake
134
Q

what does the constriction of the efferent arteriole do int he body?

A

lowers BP in peritubular capillaries enhancing reabsorption of NaCl and H2O

135
Q

what does ADH do?

A

promotes water reabsorption by collecting duct

136
Q

what is the function of the PCT?

A
  • reabsorbs about 65% of glomerular filtrate
  • removes substances from blood and secretes them into tubular fluid for disposal in urine
137
Q

how is secretion reflected in the structure and energy consumption of the PCT

A
  • long length
  • prominent microvilli
  • abundant mitochondria provide ATP for active transport
138
Q

the PCT alone account for about ___ of one’s resting ATP and calorie consumption

A

6%

139
Q

reabsorption of what molecules occurs in the PCT

A
  • glucose
  • amino acids
  • water
  • potassium
  • sodium
    bicarbonate
140
Q

what happens if blood glucose if greater than 180 mg/dl

A

not all will be reabsorbed in the PCT and will be found in the urine

141
Q

glycosuria

A

the presence of glucose in the urine

142
Q

when are amino acids commonly found in the urine?

A

after a protein-rich meal

143
Q

aminoaciduria

A

the presence of amino acids in the urine

144
Q

tubular reabsorption

A

process of reclaiming water and solutes from tubular fluid and returning them to the blood

145
Q

what ions are reabsorbed during tubular reabsorption

A
  • Na
  • K
  • Cl
146
Q

sodium-glucose transporters

A

glucose is cotransported with sodium during reabsorption

147
Q

reabsorbed fluid is ultimately taken up by

A

peritubular capillaries

148
Q

if there is glucose in urine that could indicate what disease

A

diabetes mellitus

149
Q

tubular reabsorption of nitrogenous wastes

A
  • urea reabsorbed with water
  • nephron reabsorbs about half of urea in tubular fluid
  • PCT reabsorbs nearly all uric acid
150
Q

what happens to uric acid in later portions of the nephron

A

it is secreted back into the renal tubule

151
Q

why is there such an intense reduction of urine output (180 L to 1-2 L) a day?

A

water reabsorbtion in the PCT

152
Q

____ of water in filtrate is reabsorbed in PCT

A

2/3

153
Q

reabsorption of solutes makes the tubule cells and tissue fluid ___ to tubular fluid

A

hypotonic

154
Q

obligatory water reabsorption

A

in pCT water is reabsorbed independent of hormones and at a constant rate

155
Q

peritubular capillaries reabsorb water and solutes form where?

A

that leave the basal surface of the tubular epithelium

156
Q

how does reabsorption occur in the peritubular capillaries?

A

osmosis and solvent drag

157
Q

what are the 7 steps of the effect of angiotensin 2 on tubular reabsorption

A
  • angiotensin 2 secreted
  • constricts afferent and esp efferent arterioles
  • maintains glomerular blood pressure and glomerular filtration
  • reduces BP in peritubular capillary
  • reduces resistance to tubular reabsorption
  • tubular absorption increases
  • urine volume is less but concentration is high
158
Q

tubular secretion

A

process in which renal tubule extracts chemicals from capillary blood and secretes them into the tubular fluid

159
Q

what are the three purposes of secretion in PCT and nephron loop?

A
  • acid-base balance
  • waste removal
  • clearance of drugs and contaminants
160
Q

purposes of secretion in PCT and nephron loop: acid-base balance

A

secretion of varying proportions of hydrogen and bicarbonate ions help regulate pH of body fluids

161
Q

purposes of secretion in PCT and nephron loop: waste removal

A

urea, uric acid, bile acids, ammonia, excess ions, and a little creatinine are secreted into the tubule

162
Q

purposes of secretion in PCT and nephron loop: clearance of drugs and contaminants

A

some drugs must be taken multiple times per day to keep up with renal clearance

163
Q

what drugs are excreted in the urine via secretion in PCT and nephron loop

A
  • morphine
  • penicillin
  • aspirin
164
Q

nephron loop primary function is to do what?

A

generate osmotic gradient that enables collecting duct to concentrate the urine and conserve water

165
Q

the thick segment of the nephron loop reabsorbs what

A

25% of Na, K, and Cl in filtrate

166
Q

ion reabsorption in the nephron loop occurs mostly in

A

the ascending limb

167
Q

water reabsorption in the nephron loop occurs mostly in

A

the descending limb

168
Q

ions of the nephron loop leave cells by

A

active transport and diffusion

169
Q

what happens to NaCl in the kidneys

A

it remains in the tissue fluid of renal medulla

170
Q

why can water not follow ions in the thick segment of the nephron loop

A

the thick segment is impermeable to water

171
Q

what is still in fluid as it arrives to DCT?

A
  • about 20% of water
  • 7% of salts from glomerular filtrate
172
Q

what would happen if all the fluid in the DCT passes to urine?

A

it would result in 36 L/day of urine

173
Q

what hormones regulate the reabsorption of water and salts in the DCT and collecting ducts? (4)

A
  • aldosterone
  • atrial natriuretic peptide
  • ADH
  • parathyroid hormone
174
Q

aldosterone

A
  • steroid hormone that stims reabsorption of sodium and secretion of potassium
  • secreted by adrenal cortex
175
Q

when is aldosterone secreted?

A
  • blood Na concentration falls or K concentration rises
  • drop in BP stims renin release resulting in aldosterone release
176
Q

where does aldosterone act?

A

acts on thick segment of ascending nephron loop, on the DCT, and cortical portion of collecting duct

177
Q

what happens when aldosterone acts?

A
  • stims reabsorption of Na and secretion of K
  • water and Cl follow Na
  • body retains NaCl and water as net effect
  • urine is reduced
  • urine has elevated K concentration
178
Q

what is the purpose of the body retaining NaCl

A

helps maintain blood volume and pressure

179
Q

antidiuretic hormone (ADH)

A
  • stims water retention by kidney
  • released by posterior pituitary
180
Q

when is ADH released?

A
  • dehydration
  • loss of blood volume
  • rising blood osmolarity
181
Q

what happens when ADH is released?

A

stims the arterial baroreceptors and hypothalamic osmoreceptors

182
Q

what does ADH do in the kidney?

A
  • makes the collecting duct more permeable to water to cause more water reabsorption
  • water in the tubular fluid reenters the tissue fluid and blood stream rather than being lost in urine
183
Q

what are the steps of the CD creating hypertonic urine (4)

A
  • CD begins in the cortex where it receives tubular fluid from several nephrons
  • CD runs through medulla and reabsorbs water making urine up to four times more concentrated
  • medullary portion of CD is more permeable to water than to NaCl
  • as urine passes through the increasingly salty medulla water leaves CD by osmosis concentrating urine
184
Q

urine concentration depends on what

A

the body’s state of hydration

185
Q

how does dehydration lead to production of hypertonic urine (2)

A
  • ADH stims increase in aquaporin channels in the CD to cause more water reabsorption
  • results in urine volume decrease since more concentrated
186
Q

how does hydration cause less concentrated urine (3)

A
  • ADH secretion falls and tubule cells remove aquaporins
  • CD are less permeable to water so more water remains in CD
  • results in more urine with less concentration
187
Q

ureters

A
  • retroperitoneal
  • muscular tubes that extend from each kidney to urinary bladder
  • 25 cm long
188
Q

where do the ureters enter the urinary bladder?

A

pass posterior to bladder and enter it from below

189
Q

____ acts as valve into bladder

A

flap of mucosa at entrance of each ureter

190
Q

what is the purpose of the valve at the entrance of each ureter

A

keeps urine from backing up into ureter when bladder contracts

191
Q

what is the con of the ureter lumen being very narrow

A

easily obstructed by kidneys stones

192
Q

urinary bladder

A
  • muscular sac located on floor of the pelvic cavity
  • inferior to peritoneum and posterior to pubic symphysis
193
Q

wall of urinary bladder consists of

A
  • muscularis called the detrusor
  • mucosa lined with urothelium
194
Q

detrusor

A

three layers of smooth muscle in the urinary bladder

195
Q

trigone

A

smooth triangular area marked by openings of the two ureters and the urethra

196
Q

rugae in the urinary bladder

A

conspicuous wrinkles in empty bladder

197
Q

urethra

A

tube that conveys urine out of body

198
Q

female urethra

A
  • 3-4cm long
  • bound to anterior wall of vagina
199
Q

external urethral orifice is located where

A

between vaginal orifice and clitoris

200
Q

male urethra

A
  • 18 cm long
  • three regions
201
Q

what are the three regions of the urethra?

A
  • prostatic urethra
  • membranous urethra
  • spongy urethra
202
Q

prostatic urethra

A
  • 2.5 cm
  • passes through prostate
203
Q

membranous urethra

A
  • 0.5 cm
  • passes through penis in the corpus spongiosum
204
Q

spongy urethra

A
  • penile urethra
  • 15 cm
  • passes through the penis in the corpus spongiosum
205
Q

describe how the tissue of the mucosa in the urethra changes as it gets closer to the external orifice

A
  • urothelium near the bladder
  • pseudostratified epithelium for most of its length
  • stratified squamous near external orifice
206
Q

mucous ____ are on the walls of the urethra

A

urethral glands

207
Q

what are the two urethral sphincters?

A

internal and external

208
Q

internal urethral sphincter

A
  • thickened collar of muscle around the neck of the urinary bladder and nearby urethra
  • composed with smooth muscle
209
Q

external urethral sphincter

A
  • where urethra passes through the pelvic floor
  • composed of skeletal muscle
210
Q

what happens to the detrusor when the urinary bladder fills

A

remains relaxed and urethral sphincters are closed

211
Q

micturition

A

the act of urinating

212
Q

what does micturition require?

A

relaxation of both the internal and external urethral sphincters

213
Q

contraction of ___ compresses urinary bladder to expel urine

A

detrusor muscle

214
Q

what controls the internal urethral sphincter?

A

the pons

215
Q

what controls the external urethral sphincter

A

voluntary control of skeletal muscle

216
Q

what are the four steps of the involuntary micturition reflex

A
  • stretch receptors detect filling of bladder and transmit afferent signals to spinal cord
  • signals return to bladder from spinal cord segments S2 and S3 via parasym fibers in pelvic nerve
  • efferent signals excite detrusor muscle
  • efferent signals relax internal urethral spincter
217
Q

urine is involuntarily voided when the efferent signals of the bladder relax unless what happens

A

inhibited by the brain

218
Q

what are the four steps of voluntary micturition reflex

A
  • micturition center in pons receives signals from stretch receptors
  • if timely to urinate, urination occurs
  • if untimely to urinate, urination does not occur
219
Q

if it is timely to urinate, which of what two things could happen in the voluntary micturition reflex

A
  • pons returns signals to spinal interneurons that excite detrusor and relax internal urethral sphincter
  • signals from cerebrum inhibit sacral neurons that keep external sphincter closed relaxing the external urethral sphincter and urine is voided
220
Q

if it is untimely to urinate what happens to inhibit micturition in the voluntary micturition reflex

A

signals from cerebrum excite spinal interneurons that keep urethral sphincter contracted so urine is retained in the bladder

A&P 2 (9 decks)

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