urinary system Flashcards
(112 cards)
1
Q
Describe the role of the kidneys in homeostasis.
A
The kidneys maintain a stable internal environment by regulating water-salt and acid-base balance, blood volume, blood ionic composition, and blood pH.
2
Q
How is glomerular filtration pressure regulated?
A
Glomerular filtration pressure is regulated by the balance of forces favoring filtration, such as glomerular hydrostatic pressure, and opposing forces like hydrostatic pressure in Bowman’s space and colloid osmotic pressure.
3
Q
Define glomerular filtration rate (GFR).
A
GFR is the volume of fluid filtered from the glomerulus into Bowman’s space per unit time.
4
Q
What are the main functions of the kidneys?
A
The kidneys are responsible for homeostasis, excretion of metabolic waste, regulation of blood pressure, production of hormones, and regulation of blood glucose levels.
5
Q
How do the kidneys regulate blood pressure?
A
The kidneys regulate blood pressure through the renin-angiotensin-aldosterone system (RAAS).
6
Q
Explain the significance of urine characteristics.
A
Urine characteristics such as pH, water content, volume, color, and solute composition provide insights into metabolic processes and kidney function.
7
Q
What is the typical volume of urine produced per day?
A
The typical volume of urine produced per day is approximately 1.2 liters.
8
Q
Describe the composition of urine.
A
Urine is composed of electrolytes, urea, creatinine, uric acid, and metabolic end products of hormones and other substances.
9
Q
How does the kidney contribute to the regulation of blood glucose levels?
A
The kidney contributes to blood glucose regulation through gluconeogenesis, the process of producing glucose from non-carbohydrate sources.
10
Q
What is the normal pH range of urine?
A
The normal pH range of urine is between 4.5 and 8, with an average around 6.
11
Q
Identify the metabolic wastes excreted by the kidneys.
A
The kidneys excrete metabolic wastes such as urea, uric acid, and creatinine.
12
Q
How does the kidney regulate blood osmolarity?
A
The kidneys regulate blood osmolarity by adjusting the concentration of solutes in the blood and urine.
13
Q
What is the role of erythropoietin produced by the kidneys?
A
Erythropoietin stimulates the production of red blood cells in response to low oxygen levels.
14
Q
Describe the process of activating vitamin D3 to calcitriol in the kidneys.
A
The kidneys convert vitamin D3 into calcitriol, which is the active form of vitamin D, important for calcium and phosphate metabolism.
15
Q
What are the forces that favor glomerular filtration?
A
The forces that favor glomerular filtration include glomerular hydrostatic pressure (P_GC), which pushes plasma out of the capillary.
16
Q
What are the opposing forces to glomerular filtration?
A
The opposing forces to glomerular filtration include hydrostatic pressure in Bowman’s space (P_BS) and colloid osmotic pressure due to proteins in plasma (π_GC).
17
Q
Calculate the net glomerular filtration pressure.
A
Net glomerular filtration pressure is calculated as P_GC – (P_BS + π_GC).
18
Q
Describe the daily glomerular filtration rate for a 70-kg adult.
A
The daily glomerular filtration rate for a 70-kg adult is approximately 180 liters per day, which equates to about 125 ml/min.
19
Q
How does the kidneys regulate plasma composition?
A
The kidneys regulate plasma composition rapidly and excrete large quantities of waste products through the process of glomerular filtration.
20
Q
Define filterable and non-filterable blood components.
A
Filterable blood components include water, nitrogenous waste, nutrients, and ions, while non-filterable components include blood cells, platelets, and plasma proteins.
21
Q
What factors influence glomerular filtration rate (GFR)?
A
GFR is influenced by net glomerular filtration pressure, adequate circulation, and blood pressure.
22
Q
Explain the role of myogenic regulation in glomerular filtration.
A
Myogenic regulation involves smooth muscle mediated through stretch receptors preceding the glomerulus, which helps maintain GFR despite changes in blood pressure.
23
Q
How does the renin-angiotensin-aldosterone system (RAAS) respond to low blood pressure?
A
When blood pressure is low, the juxtaglomerular apparatus releases renin, which catalyzes reactions that produce angiotensin II, leading to vasoconstriction and increased blood pressure.
24
Q
What is the effect of angiotensin II on the kidneys?
A
Angiotensin II increases capillary pressure within the glomerulus, which enhances GFR, promotes water retention, and increases sodium reabsorption.
25
Describe the function of atrial natriuretic peptide (ANP).
ANP opposes the actions of angiotensin II and inhibits the release of aldosterone, helping to lower blood pressure when high sodium levels are detected in the heart.
26
How does the juxtaglomerular apparatus (JGA) respond to low sodium levels?
The JGA releases renin into the blood when low sodium levels, low blood pressure, or low chloride levels are detected.
27
What is the relationship between blood volume and blood pressure in the context of RAAS?
A decrease in blood volume leads to a decrease in blood pressure, which triggers the JGA to release renin, activating the RAAS to restore blood pressure.
28
Describe the role of aldosterone in sodium and potassium balance.
Aldosterone, produced by the adrenal cortex, promotes sodium reabsorption in exchange for potassium, which helps regulate blood pressure and fluid balance.
29
How does low aldosterone levels affect urine volume and concentration?
Low aldosterone levels prevent sodium reabsorption, leading to increased water excretion and a larger volume of dilute urine.
30
Define the process of water reabsorption in the renal tubule.
Water reabsorption in the renal tubule controls urine volume, with 70% reabsorbed in the proximal tubule, 20% in the distal tubule, and 10% in the collecting ducts.
31
Explain the function of ADH in the kidneys.
ADH stimulates the insertion of aquaporin-2 water channels in the principal cells of the collecting ducts, increasing water reabsorption and reducing urine volume.
32
What is the effect of ADH on urine concentration?
ADH prevents excessive water loss, leading to a smaller volume of concentrated urine.
33
How does diabetes insipidus affect water balance in the body?
Diabetes insipidus results from a lack of ADH release, causing severe dehydration and electrolyte imbalances due to excessive water loss in urine.
34
Summarize the role of the kidneys in homeostasis.
The kidneys maintain homeostasis by regulating blood pressure, blood volume, and the concentration of urine through mechanisms like the renin-angiotensin-aldosterone system and ADH secretion.
35
Differentiate between obligatory and facultative water reabsorption.
Obligatory water reabsorption occurs along the proximal tubule and descending loop of Henle and is not adjustable, while facultative water reabsorption is regulated by ADH in the distal tubule and collecting ducts.
36
Describe the impact of the renin-angiotensin-aldosterone system (RAAS) on blood pressure.
RAAS plays a crucial role in regulating blood pressure and blood volume by adjusting sodium and water reabsorption in the kidneys.
37
How does the ascending loop of Henle contribute to urine concentration?
The ascending loop of Henle is impermeable to water, which means no water reabsorption occurs there, contributing to the dilution of urine.
38
Describe the processes involved in tubular reabsorption in the urinary system.
Tubular reabsorption involves the movement of substances from the renal tubule cells back into the peritubular capillaries, including water, glucose, amino acids, and ions. Most reabsorption occurs in the proximal convoluted tubule and can be both passive and active.
39
Define glomerular filtration and its significance in urine formation.
Glomerular filtration is the process that results in the formation of filtrate, which is plasma minus most plasma proteins. It is the first step in urine formation and occurs across three filtration barriers: the fenestrated endothelium, the basal membrane, and the surrounding epithelial cell layer.
40
How do peritubular capillaries contribute to the renal exchange process?
Peritubular capillaries reabsorb useful substances from the renal tubule cells, such as water, glucose, amino acids, and ions, facilitating the recovery of essential nutrients and maintaining fluid balance.
41
Explain the role of secretion in the renal tubules.
Secretion in the renal tubules involves the active transport of substances from the blood into the tubular fluid, allowing for the elimination of waste products and the regulation of electrolyte balance.
42
Describe the mechanism of water reabsorption in the renal tubules.
Water reabsorption is driven by osmolarity differences; as solutes are actively reabsorbed, they increase the osmolarity of plasma, causing water to diffuse from the tubular fluid into the plasma.
43
What are the three filtration barriers in the glomerular membrane?
The three filtration barriers in the glomerular membrane are the fenestrated endothelium, the basal membrane, and the surrounding epithelial cell layer.
44
How does active reabsorption differ from passive reabsorption in the renal tubules?
Active reabsorption requires energy to transport substances against their concentration gradient, while passive reabsorption occurs without energy expenditure, relying on concentration gradients.
45
Identify the primary site of tubular reabsorption in the nephron.
The primary site of tubular reabsorption in the nephron is the proximal convoluted tubule.
46
What substances are primarily filtered and reabsorbed in the urinary system?
Substances primarily filtered include water, glucose, amino acids, and ions, with most of these being reabsorbed in the proximal convoluted tubule.
47
How does the osmolarity of plasma affect water reabsorption in the kidneys?
As solutes are reabsorbed and increase the osmolarity of plasma, water diffuses from the tubular fluid into the plasma to balance osmotic pressures.
48
Describe the process of glucose reabsorption in the kidneys.
Glucose is freely filtered at the glomerulus and is normally 100% actively reabsorbed in the proximal tubule, resulting in no glucose appearing in urine.
49
How do molecules move during tubular secretion?
Molecules move from the plasma of peritubular capillaries into the renal tubules to become part of the filtrate, following similar processes as reabsorption but in the reverse direction.
50
Define tubular reabsorption.
Tubular reabsorption is the process by which substances are reabsorbed from the filtrate back into the blood, including ions, metabolites, and water.
51
What is the end result of tubular secretion?
The end result of secretion is an increase in the quantity of solute excreted in the urine, which decreases the solute’s plasma concentration.
52
List some substances that are actively secreted in the renal tubules.
Potassium ions, hydrogen ions, waste products like choline and creatinine, and foreign substances such as the antibiotic penicillin.
53
Explain the significance of excretion in the body.
Excretion is the elimination of solute and water from the body in the form of urine, which directly affects the volume and composition of plasma.
54
Identify the ions that are typically reabsorbed in the kidneys.
Ions that are reabsorbed include Na+, Cl-, K+, Ca2+, Mg2+, SO42-, and HCO3-.
55
What happens to glucose in the urine under normal conditions?
Under normal conditions, no glucose appears in urine because it is completely reabsorbed in the proximal tubule.
56
How does the body handle waste products during tubular secretion?
Waste products such as creatinine and ammonia are secreted from the plasma into the renal tubules to be excreted in urine.
57
Describe the role of tubular reabsorption and secretion in kidney function.
Tubular reabsorption and secretion are crucial for regulating the composition of blood, maintaining electrolyte balance, and eliminating waste products.
58
Describe the simple rule of excretion in the renal system.
Material that enters the lumen of the renal tubules is excreted unless it is reabsorbed.
59
How can substances enter the renal tubules?
Substances can enter renal tubules either by filtration or by secretion.
60
Define the expression for the quantity of a substance excreted in urine.
The quantity of a substance excreted in urine is given by the expression: Amount excreted = amount filtered + amount secreted - amount reabsorbed (E = F + S - R).
61
Explain the process of reabsorption in the renal tubules.
Reabsorption occurs via a mixture of diffusion and active transport.
62
What role does each segment of the renal tubule play?
Each segment of the renal tubule has a role in reabsorption and secretion.
63
Define transport maximum in the context of renal function.
Transport maximum is the concentration of a substance when carriers are saturated, reflecting the number of carriers available.
64
What happens to nutrients when they exceed the transport maximum?
Nutrients will normally be fully reabsorbed unless they exceed the transport maximum (Tm) or there is a pathological condition.
65
What is the renal threshold?
The renal threshold is the plasma concentration at which a specific substance or ion begins to appear in urine.
66
How do different substances vary in terms of transport maximum and renal thresholds?
Different substances have different transport maximums (Tm) and different renal thresholds.
67
What is the renal threshold for amino acids?
The renal threshold for amino acids is 65 mg/dL.
68
What is the renal threshold for glucose?
The renal threshold for glucose is 180 mg/dL.
69
Describe the anatomy of the nephron.
The nephron consists of the renal corpuscle and renal tubules, including Bowman’s capsule, proximal tubule, loop of Henle (with descending and ascending limbs), distal tubule, and collecting duct.
70
Define the two types of nephrons.
Cortical nephrons have a short loop of Henle and make up 80-85% of nephrons, while juxtamedullary nephrons have a long loop of Henle that extends into the medulla and are responsible for the medullary osmotic gradient.
71
72
How does blood flow through the renal corpuscle?
Blood enters through the renal artery, flows via afferent arterioles into the glomerulus, where approximately 20% of plasma leaks into Bowman’s space, and the remainder exits via efferent arterioles.
73
Describe the structure of Bowman’s capsule.
Bowman’s capsule is an invaginated sphere that forms two layers: the parietal layer (outer) and the visceral layer (inner), playing a role in the production of filtrate.
74
What is the role of the glomerular capillary?
The glomerular capillary has a fenestrated endothelium that allows for the filtration of plasma into Bowman’s space, contributing to the formation of urine.
75
How do podocytes contribute to filtration in the nephron?
Podocytes are visceral epithelial cells that form the filtration slit diaphragm, which helps regulate the passage of substances from the blood into Bowman’s space.
76
Describe the function of the proximal convoluted tubule.
The proximal convoluted tubule is lined with cuboidal epithelial cells and is responsible for the reabsorption of water, ions, and nutrients from the filtrate back into the bloodstream.
77
What is the significance of the loop of Henle in nephron function?
The loop of Henle, consisting of descending and ascending limbs, plays a crucial role in concentrating urine and maintaining the medullary osmotic gradient.
78
How does the nephron contribute to urine production?
Both types of nephrons (cortical and juxtamedullary) are involved in the processes of filtration, reabsorption, and secretion, ultimately leading to urine production.
79
Define the glomerular basement membrane (GBM).
The glomerular basement membrane is a mesh of extracellular proteins that provides structural support and plays a key role in the filtration process within the renal corpuscle.
80
Describe the function of the brush border in the renal tubule.
The brush border allows for the reabsorption of filtrate components, including 70% of water and sodium, and 100% of glucose.
81
How does the structure of the proximal convoluted tubule (PCT) facilitate its function?
The PCT has a brush border, is rich in mitochondria, and contains tight junctions that allow for paracellular transport.
82
Define the characteristics of the distal convoluted tubule (DCT).
The DCT is lined with simple cuboidal epithelium, has no brush border, and contains a high proportion of mitochondria, though fewer than the PCT.
83
What is the role of the collecting duct in the renal system?
The collecting ducts merge and become larger as they descend through the medulla, playing a crucial role in the final concentration of urine.
84
Explain the function of the juxtaglomerular apparatus.
The juxtaglomerular apparatus regulates blood pressure and the filtration rate of the glomerulus.
85
Describe the macula densa and its function.
The macula densa is a densely packed group of modified epithelial cells in the DCT that detect and regulate sodium ion concentration.
86
What are juxtaglomerular cells and their role in blood pressure regulation?
Juxtaglomerular cells, derived from smooth muscle cells of the afferent arteriole, secrete renin and regulate blood pressure via the renin-angiotensin-aldosterone system.
87
Summarize the structure of the nephron.
The nephron is divided into the renal corpuscle and renal tubules, which can be further divided into specialized regions with distinct epithelia.
88
How is the loop of Henle structured?
The loop of Henle has a descending limb with epithelium similar to the PCT, while both the thin ascending and descending limbs are lined by simple squamous epithelium, and the thick ascending limb is lined by cuboidal epithelium similar to the DCT.
89
Describe the urinary system.
The urinary system, also known as the renal system, consists of the kidneys, ureters, bladder, and urethra, which work together to remove waste products from the body and regulate various aspects of blood composition.
90
Define the main functions of the urinary system.
The main functions of the urinary system include the removal of metabolic waste products and foreign substances from the plasma, regulation of plasma ionic composition, plasma volume and blood pressure, plasma osmolarity, and plasma hydrogen ion concentration (pH).
91
How are the kidneys positioned in the body?
The kidneys lie retro-peritoneally in the back abdominal wall.
92
Describe the anatomy of the kidney.
The kidney consists of three main regions: the renal cortex, which is an outer granulated layer; the renal medulla, which contains cone-shaped tissue masses called renal pyramids; and the renal pelvis, which contains major renal blood vessels and is where the ureter originates.
93
What is the role of the ureters in the urinary system?
The ureters conduct urine from the kidneys to the bladder.
94
Explain the function of the bladder.
The bladder is an expandable organ that stores urine until it is expelled from the body.
95
What is the purpose of the urethra?
The urethra excretes urine from the bladder to the outside of the body.
96
Define the nephron.
The nephron is the microscopic functional unit of the kidney that filters blood and produces urine.
97
What are the two types of nephrons?
The two types of nephrons are cortical nephrons and juxtamedullary nephrons.
98
Describe the structure of a nephron.
A nephron consists of two main parts: the renal corpuscle and the tubules, which include Bowman’s capsule, proximal tubule, distal tubule, collecting duct, and the loop of Henle.
99
What are the components of the renal corpuscle?
The renal corpuscle is made up of Bowman’s capsule and the glomerulus.
100
How does the loop of Henle function in the nephron?
The loop of Henle consists of a descending limb and an ascending limb, which play a crucial role in the concentration of urine and the reabsorption of water and salts.
101
What is the significance of the renal pelvis?
The renal pelvis is significant as it contains the major renal blood vessels and is the region from which the ureter originates.
102
Describe the two types of nephrons.
Cortical nephrons and juxtamedullary nephrons.
103
How do kidneys receive blood supply?
Each kidney receives blood through a renal artery, which enters at the hilus directly from the aorta.
104
Define the role of glomerular capillaries in the kidney.
Glomerular capillaries converge to form the efferent arterioles, which lead to the peritubular capillaries.
105
What is the function of the vasa recta?
The vasa recta are straight vessels that wrap around the loop of Henle and are involved in draining blood.
106
Explain the pathway of blood drainage from the kidney.
Blood drains from the vasa recta into the interlobular vein, then to the arcuate vein, interlobar vein, renal vein, and finally into the inferior vena cava.
107
Identify the four organs that compose the urinary system.
The urinary system is composed of the kidneys, bladder, ureters, and urethra.
108
How does the renal artery branch in the kidney?
The renal artery branches into five segmental arteries, which further branch into interlobar arteries.
108
What are the three parts of the kidney?
The kidney is divided into the renal cortex, renal pelvis, and renal medulla.
109
Describe the blood supply network surrounding the renal tubule.
The blood supply to the kidney is a complex network that includes afferent arterioles, glomerular capillaries, efferent arterioles, and peritubular capillaries.
110
What percentage of cardiac output do the kidneys receive?
The kidneys receive 20-25% of the total cardiac output.
111
Describe the relationship between interlobar arteries and arcuate arteries.
Interlobar arteries branch into arcuate arteries.
