🌱 MCAT Biology Review - 10 Flashcards
(118 cards)
1
Q
Which structure in the kidney is responsible for filtering blood?
A
Glomerulus
2
Q
In which segment of the nephron is sodium NOT actively transported out?
A
Thin portion of the ascending limb of the loop of Henle
3
Q
What is the primary function of the nephron under normal physiological circumstances?
A
To create urine that is hypertonic to the blood.
4
Q
Which layer of the skin contains the stem cells of keratinocytes?
A
Stratum basale
5
Q
True or False: ADH acts directly on the proximal convoluted tubule.
A
False
6
Q
What process allows amino acids to enter the vasa recta in the nephron?
A
Reabsorption
7
Q
What is the main role of the kidneys in the excretory system?
A
Regulation of blood pressure, blood osmolarity, acid-base balance, and removal of nitrogenous wastes.
8
Q
What is the structure that collects urine from the nephrons before it moves to the ureter?
A
Renal pelvis
9
Q
What type of muscle is the detrusor muscle in the bladder?
A
Smooth muscle
10
Q
Fill in the blank: The _______ sphincter is under involuntary control.
A
Internal urethral
11
Q
Fill in the blank: The _______ sphincter consists of skeletal muscle.
A
External urethral
12
Q
What happens to the internal sphincter during the micturition reflex?
A
It relaxes
13
Q
What is the role of the vasa recta in the renal vascular system?
A
To surround the loop of Henle and facilitate solute exchange.
14
Q
What common over-the-counter drug can lead to analgesic nephropathy when used excessively?
A
Ibuprofen
15
Q
True or False: The kidneys have one of the few portal systems in the body.
A
True
16
Q
Which system in the body connects the hypothalamus and the anterior pituitary?
A
Hypophyseal portal system
17
Q
What happens to blood during dialysis?
A
It is filtered to purify and excrete wastes.
18
Q
What is the micturition reflex?
A
A reflex that causes parasympathetic neurons to fire, contracting the detrusor muscle and relaxing the internal sphincter.
19
Q
What happens when the bladder is full?
A
The micturition reflex is triggered, leading to detrusor muscle contraction and internal sphincter relaxation.
20
Q
What role does abdominal musculature play in urination?
A
It increases pressure within the abdominal cavity, compressing the bladder and increasing urine flow rate.
21
Q
What is osmoregulation?
A
The process by which the kidneys filter blood to form urine, regulating blood volume and osmolarity.
22
Q
What are the three primary processes of kidney function?
A
- Filtration
- Secretion
- Reabsorption
23
Q
What is the first function of the nephron?
A
Filtration of blood.
24
Q
What is filtrate?
A
The collected fluid filtered from blood into Bowman’s space, similar in composition to blood but lacking cells and proteins.
25
What determines the movement of fluid into Bowman's space?
Starling forces, which account for pressure differentials between blood and Bowman's space.
26
What occurs if the ureter is obstructed by a kidney stone?
Increased hydrostatic pressure in Bowman's space can prevent filtration.
27
What does the presence of blood cells or proteins in urine indicate?
A health problem at the level of the glomerulus.
28
What substances are secreted by the nephrons?
* Salts
* Acids
* Bases
* Urea
29
What is the mnemonic for major waste products excreted in urine?
Dump the HUNK: H+, Urea, NH3, K+.
30
What occurs in the proximal convoluted tubule (PCT)?
Reabsorption of amino acids, glucose, water-soluble vitamins, and the majority of salts.
31
What is the primary function of the loop of Henle?
To reabsorb water and salts, concentrating urine.
32
What is the permeability of the descending limb of the loop of Henle?
Permeable only to water.
33
What happens to the osmolarity in the medulla as the descending limb of the loop of Henle travels deeper?
It increases, favoring the outflow of water from the descending limb.
34
What is the function of the ascending limb of the loop of Henle?
Permeable to salts and impermeable to water, maximizing salt reabsorption.
35
What is the diluting segment in the loop of Henle?
The thicker portion of the ascending limb where the filtrate becomes hypotonic.
36
What does the distal convoluted tubule (DCT) respond to?
Aldosterone, promoting sodium reabsorption.
37
What is the role of diuretics in kidney function?
They inhibit sodium reabsorption, increasing sodium and water excretion.
38
What regulates the final concentration of urine?
The permeability of the collecting duct, influenced by aldosterone and ADH.
39
What happens to water reabsorption during hydration?
The collecting duct becomes impermeable to salt and water.
40
What is the point of no return in urine formation?
The collecting duct, where anything not reabsorbed will be excreted.
41
What is the role of the collecting duct in the nephron?
The collecting duct is the point of no return for reabsorption; anything not reabsorbed will be excreted.
42
What hormones increase water reabsorption in the collecting duct?
ADH (antidiuretic hormone) and aldosterone.
43
What fluid is collected in the renal pelvis?
Fluid that carries mostly urea, uric acid, and excess ions (sodium, potassium, magnesium, and calcium).
44
How do the kidneys control blood pressure?
By selectively eliminating water and solutes, which affects blood volume and pressure.
45
What effect does aldosterone have on blood pressure?
Aldosterone increases blood pressure by increasing the reabsorption of sodium.
46
What are ACE inhibitors and how do they work?
ACE inhibitors block angiotensin-converting enzyme, limiting aldosterone release and reducing blood pressure.
47
What is the function of ADH?
ADH governs water reabsorption, resulting in lower blood osmolarity.
48
What does aldosterone alter in the nephron?
Aldosterone alters the ability of the distal convoluted tubule and collecting duct to reabsorb sodium.
49
How does water move in relation to sodium reabsorption?
Water travels down its osmolarity gradient; if sodium is reabsorbed, water will follow.
50
What is the bicarbonate buffer system responsible for?
Regulating blood pH.
51
What happens when blood pH is too low?
The kidneys excrete more hydrogen ions and increase reabsorption of bicarbonate.
52
What is the primary role of carbonic anhydrase II (CAII)?
CAII catalyzes the reversible hydration of carbon dioxide into carbonic acid.
53
Where is aquaporin-1 (AQP1) expressed?
In the proximal tubule and the thin descending limb of the loop of Henle.
54
What effect does CAII deficiency have on urine?
CAII-deficient mice produce dilute urine and have high urine volume.
55
Fill in the blank: The osmolarity of blood is usually maintained at approximately _______ milliosmoles per liter.
290
56
What are the three processes of solute exchange between the filtrate and the blood?
* Filtration
* Reabsorption
* Secretion
57
List the structures in the excretory pathway from where filtrate enters the nephron to the excretion of urine.
* Bowman’s capsule
* Proximal convoluted tubule
* Loop of Henle
* Distal convoluted tubule
* Collecting duct
* Renal pelvis
* Ureter
* Bladder
* Urethra
58
What are the predominant cell types in the epidermis?
Keratinocytes.
59
What are the layers of the skin starting from the deepest?
* Hypodermis (subcutaneous layer)
* Dermis
* Epidermis
60
What is the largest organ in the human body by weight and size?
Skin (integument).
61
True or False: The skin makes up about 16 percent of total body weight.
True.
62
What is the largest organ in our bodies?
Skin
## Footnote
Skin makes up about 16 percent of total body weight, on average.
63
What are the three main layers of the skin?
* Hypodermis (subcutaneous layer)
* Dermis
* Epidermis
64
What is the predominant cell type in the epidermis?
Keratinocytes
65
List the layers of the epidermis from deepest to superficial.
* Stratum basale
* Stratum spinosum
* Stratum granulosum
* Stratum lucidum
* Stratum corneum
66
What is the function of the stratum basale?
Responsible for proliferation of keratinocytes
67
What happens to keratinocytes in the stratum granulosum?
They die and lose their nuclei
68
True or False: The stratum lucidum is present in thick, hairless skin.
True
69
What is the purpose of the stratum corneum?
Forms a barrier that prevents invasion by pathogens and loss of fluids and salt
70
What do melanocytes produce?
Melanin
71
How do melanocytes affect skin color?
Varying levels of activity result in different skin tones
72
What are Langerhans cells?
Special macrophages that present antigens to T-cells
73
What are the two layers of the dermis?
* Papillary layer
* Reticular layer
74
What is the function of Merkel cells?
Responsible for deep pressure and texture sensation within the skin
75
What is the hypodermis primarily composed of?
Connective tissue and fat
76
What is thermoregulation?
The maintenance of a constant body temperature
77
What are the mechanisms the body uses to cool itself?
* Sweating
* Vasodilation
78
What is the main cooling mechanism of sweating?
Evaporation of water from the skin
79
What occurs during piloerection?
Hairs stand up to trap heated air near the skin
80
What type of muscle is the internal urethral sphincter made of?
Smooth muscle
81
What is the role of aldosterone?
Increases sodium reabsorption in the distal convoluted tubule and collecting duct
82
What is the role of antidiuretic hormone (ADH)?
Increases the permeability of the collecting duct to water
83
Fill in the blank: The epidermis is derived from the _______.
Ectoderm
84
What is the function of the dermis?
Contains sweat glands, blood vessels, and hair follicles
85
What is a callus?
Excessive keratin deposition in areas of repeated strain
86
What is the significance of brown fat?
Releases more heat energy as fuel is burned
87
What is the primary function of the skin in relation to water?
Maintains osmolarity by preventing water loss
88
What is the effect of cold conditions on blood vessels in the skin?
Arterioles constrict, limiting blood flow to the skin
89
What are the two layers of the dermis?
The papillary layer and the reticular layer.
90
Name sensory cells located in the dermis.
* Merkel cells (deep pressure and texture)
* Free nerve endings (pain)
* Meissner's corpuscles (light touch)
* Ruffini endings (stretch)
* Pacinian corpuscles (deep pressure and vibration)
91
What does the hypodermis contain?
Fat and connective tissue.
92
What is the skin's role in thermoregulation?
It maintains a constant internal temperature.
93
Fill in the blank: Cooling mechanisms include _______ and vasodilation.
sweating
94
What is the function of sweat glands?
They are innervated by postganglionic cholinergic sympathetic neurons.
95
What are warming mechanisms of the body?
* Piloerection
* Vasoconstriction
* Shivering
* Insulation provided by fat
96
What does the skin prevent?
Dehydration and salt loss from the body.
97
What is the pathway of filtrate in the kidney starting from Bowman's space?
Bowman's space ➔ proximal convoluted tubule ➔ descending limb of the loop of Henle ➔ ascending limb of the loop of Henle ➔ distal convoluted tubule ➔ collecting duct ➔ renal pelvis ➔ ureter ➔ bladder ➔ urethra
98
What is the sequence of blood flow through the kidney?
Renal artery ➔ afferent arteriole ➔ glomerulus ➔ efferent arteriole ➔ vasa recta ➔ renal vein
99
What causes contraction of the detrusor muscle?
The parasympathetic nervous system.
100
Define filtration in the context of kidney function.
The movement of solutes from blood into filtrate at Bowman's capsule.
101
Define secretion in kidney function.
The movement of solutes from blood into filtrate anywhere besides Bowman's capsule.
102
Define reabsorption in kidney function.
The movement of solutes from filtrate into blood.
103
What does Bowman's capsule do?
It is the site of filtration, allowing water, ions, amino acids, vitamins, and glucose to pass.
104
What is the function of the proximal convoluted tubule?
It controls solute identity, reabsorbing vitamins, amino acids, and glucose while secreting potassium and hydrogen ions, ammonia, and urea.
105
What is the role of the descending limb of the loop of Henle?
It is important for water reabsorption.
106
What is the role of the ascending limb of the loop of Henle?
It is important for salt reabsorption and dilution of urine.
107
What does the distal convoluted tubule do?
It is important for solute identity by reabsorbing salts and secreting potassium and hydrogen ions, ammonia, and urea.
108
What is the function of the collecting duct?
It is important for urine concentration; its variable permeability allows water to be reabsorbed based on the body's needs.
109
What are keratinocytes?
The primary cells of the epidermis.
110
List the layers of the epidermis.
* Stratum corneum
* Stratum lucidum
* Stratum granulosum
* Stratum spinosum
* Stratum basale
111
What is the primary function of the nephron?
To create urine that is hypertonic to the blood.
112
True or False: The glomerulus allows large proteins to pass through.
False
113
What happens when blood pH is high?
The kidney increases excretion of a base, namely bicarbonate.
114
Where do stem cells that form keratinocytes reside?
In the stratum basale.
115
What does aldosterone do?
It increases reabsorption of sodium and promotes excretion of potassium and hydrogen ions.
116
How does the hypothalamus regulate body temperature?
It acts as a thermostat, causing blood vessels to constrict and stimulating shivering.
117
What is the significance of the vasa recta?
It reabsorbs various ions and envelops the nephron tubule.
118
Fill in the blank: An excess of _______ will lead to increased urination.
acetylcholine
