Excretory System Flashcards
1
Q
What are the functions of the excretory system?
A
- excretion: waste products, most are metabolic by products of cells and substances absorbed from the intestine.
- regulation of blood, volume and pressure: large volume of dilute urine or A small volume of concentrated urine.
- regulation of solute concentration in the blood: glucose, sodium, chloride, potassium, calcium, bicarbonate, phosphate.
- regulation of extracellular fluid pH: the kidneys excrete variable amounts of hydrogen ions.
-
regulation of red blood cells ( RBC) synthesis: erythropoietin hormone
-** regulation of vitamin D synthesis**
2
Q
What is the main excretory product in humans?
A
urea.
It is generated by the breakdown of proteins in the liver where the excess amino acids are converted into urea.
The urea is excreted out of the body via urine.
3
Q
What is a ureter ?
A
A tube leading urine from the kidney to the bladder.
4
Q
What is a urethra?
A
The urethral tube from which urine exits
5
Q
What are sphincter muscles?
A
met also have inner part to the muscle which prevents sperm from entering.
Muscles found between the urethra and the blade and controls urination.
Both smooth and striated muscle.
The activation of the internal muscle of men is under autonomic control.
6
Q
Where does most of the reabsorption into the bloodstream occur?
A
In the proximal tube, which consists of cuboidal cells with microvilli, tight junctions and many mitochondria.
7
Q
What does the GFR measure?
A
The rate at which fluid are filtered from the blood into the glomerulus.
8
Q
What is the difference between the component of ultrafiltrate fluid and plasma fluid?
A
The components of the plasma fluid and the ultrafiltrate fluid are almost identical, the difference between them is the much higher protein concentration in the plasma.
9
Q
What are podocyte?
A
Cells in Bowman’s capsule in the kidneys that wrap around capillaries of the glomerulus. Podocytes make up the epithelial lining of Bowman’s capsule ( the third layer ), through which filtration of blood takes place.
10
Q
Describe the proximal convoluted tube
A
- Starts after capsule toe
- it’s cells contain microvilli
- most of the reabsorption occurs in it
- has a lot of mitochondria
- contains Na, K pumps on the basal side that take Na out of the cell into the blood, which creates a gradient that helps substances that the body wants to enter.
11
Q
What is the function of the proximal convoluted tubule?
A
The PCT is responsible for reabsorbing most of the glucose, amino acids, and small peptides that enter the ultrafiltrate
12
Q
What is the glomerulus?
A
A network of capillaries from which the main drainage of blood to the nephron takes place
13
Q
What is the peritoneum?
A
Close membrane that surrounds the abdominal organs
14
Q
Where are the kidneys located in relation to the peritoneum?
A
Behind it, they are actually outside the peritoneal cavity.
The kidneys are situated below the diaphragm, one on either side of the spine.
15
Q
What are interlobar arteries?
A
Arteries that branch Off from the renal artery and are between lobes ( renal pyramid) of the kidneys.
16
Q
What are renal pyramids?
A
Renal pyramids are small shaped like cones structures that contain strings of nephrons and tubules.
These tubules transport fluid into the kidney. This fluid then moves away from the nephrons toward the inner structures that collect and transport urine out of the kidney.
# Another term for renal pyramids is malpighian pyramids.
In humans there are 7 pyramids (in the medulla).
17
Q
What is the route of the arcuate arteries?
A
They emerge from the bifurcations of the interlobular arteries and are located between the medulla and the cortex
18
Q
What is the route of the interlobular arteries?
A
Between the lobes.
Pass between the renal pyramids anegive rise to the arcuate (Arched) arteries - they branch Off the arcuate arteries and project into cortex.
19
Q
What is the route of the afferent artioles?
A
The afferent artioles arise from branches of the interlobular arteries and extend to the glomerular capillaries
20
Q
What is the route of the efferent arterioles?
A
Extend from the glomerular capillaries to the peritubuIar
21
Q
What is the route of the peritubular capillaries?
A
Around the tubes.
Surround the proximal and distal convoluted tubules and the loops of helne.
22
Q
What is the vasa recta?
A
Straight vessels.
Specialized portions of the peritubular capillaries flat extend deep into the medulla of the kidney and surround the loops of Helne and collecting ducts.
23
Q
What is the total route of the blood vessels in the excretory system?
A
Abdominal aorta > renal arteries ( enter kidneys) > interlobar arteries & Afferent arterioles > glomerular capillaries > efferent arterioles > peritubulan capillaries ( & vasa recta )> intertabular veins
24
Q
What is the juxtaglomerular apparatus?
A
A structure that is formed where the distal convoluted tubule comes in contact with the afferent arterioles next to the bowman capsule.
It consists of specialized cells of the walls of the afferent arterioles and the distal convoluted tubules.
Certain cells called granular cells secrete the enzyme renin.
25
What is the pubic symphysis?
The attachment points of the pelvic bones (the one not in the spine)
26
What will happen when sympathetic stimulus occurs in terms of pressure in the glomerulus?
Decreased pressure.
In dangerous situations there is no need to urinate.
27
Do aquaporins exists in the proximal convoluted tubule?
Yes
28
Where does 65% of the reabsorption of water in nephron occur?
Proximal convoluted tubule.
29
Is there a difference between the ion concentration in the proximal convoluted tubule and that in the blood?
No
30
Where is the filtrate more concentrated, In the beginning or in the end of the loop of Henle?
In the beginning (the descending limb ), where the water moves out of the neuron though osmosis.
31
What is the concentration of the intercellular fluid in the kidney?
It is between 300 in the cortex and 1200 in the inner medulla.
32
Which part of the nephron has microvilli brush border?
Proximal convoluted tubule.
33
What happens to amino acids in the liver?
They go through a process called deamination.
During this process, water molecules and amino acids are consumed and keto acid is formed.
34
Is the ascending loop of henIe permeable to urea?
Yes
35
What change is ADH sensitive to?
Blood concentration
36
What Change is ANH sensitive to?
Blood pressure
37
Where is renin secreted from?
Juxtaglomerular apparatres in the kidney - by the granular cells.
38
Where is angiotensinagen secreted from?
Liver
39
Where ave the enzymes ACE that turn angiotensin 1 to angiotensin 2 secrete from?
Lungs
40
Where is aldosterone secreted from?
From the adrenal gland.
41
What activated the secretion of aldosterone?
Angiotensin 2
42
What is PTH?
Parathyroid hormone
Secreted by the parathyroid glands.
Responsible for increasing the concentration of Ca in the extracellular fluid, by activating osteoclasts which breaks down bone and by increasing the absorption of Ca from the nephrons .
43
What does the excretory system consist of?
2 kidneys
2 ureters
Urinary bladder
Urethra
44
Define kidneys
- Thousands of tiny tubes called nephrons make up the structure.
- Bean shaped organs
- The size of a tightly clenched fist
- located on the posterior abdominal wall
- retroperitoneal
- layers of the kidney →
* renal capsule: surrounds each kidney
* adipose tissue: thick layer, around the renal capsule.
* renal facia
- each kidney receives blood from a renal artery and return blood via renal veins
45
What we the layers inside of the kidneys?
- Cortex - outer layer
- medulla - inner layer
# they surround the renal sinus
- renal pyramid - located at the boundary between the cortex and the medulla and the tips of the renal pyramids project toward the center of the kidneys
- calyx ( calyces ) - funnel shape structure surround the tip of each renal pyramid and are joined to form a larger funnel
- renal pelvis - the lawyer funnel formed from the calyces. Later, narrows to form the ureter
46
What is The urinary tract?
Tips of renal pyramids > calyces > renal pelvis > ureter (exit kidney) > urinary bladder > urethra
47
What is the hilum?
- On the medial side of each kidney
- where the renal artery and nerves enter & where the renal vein, ureter and lymphatic vessels exit the kidney.
48
Define nephron
- The functional unit of the kidney.
- approximately 1.3 million in each kidney
- each nephron consist:
* renal corpuscle
* proximal convoluted tubule
* loop of Helne
* distal convoluted tubule
49
Describe the route of fluid inside a nephron
Fluid is force tinto the renal corpuscle > proximal convoluted tubule > descending limb ( loop)- toward the renal sinus > ascending limb (loop) - toward the cortex > distal convoluted tubule > collecting duct - from cortex to medulla > papillary duct > calyx
50
Where is the renal corpuscle located?
Renal cortex
51
Where are the convoluted tubules located?
Renal cortex
52
Where is the collecting duct located?
Medulla
53
Where is the loop of Henle located?
Medulla
54
What does the renal corpuscle consist of?
Bowman capsule
Glomerulus
55
What does the bowman capsule consist of?
- Enlarged end of the nephron, which is intended to form a double walled chamber.
- Inside the glomerulus.
- The cavity of the bowman capsule opens into the proximal convoluted tubule.
- The inner layer consist of specialized cells called podocytes (wrap around the glomerulus)
- the outer layer consist of simple squamous epithelial cells.
56
Describe the filtration membrane
Fenestrated endothelium → each endothelial cell her thousand of tiny holes
Basement membrane → composed of a network of collagen and glycoproteins
Podocytes → have many look-like processes separated by gaps, called filtration slits
57
What is filtrate?
A Fluid, consisting of water and solutes smaller than proteins, that pass from the blood in the glomerulus capillaries through the filtration membrane into the bowman capsule.
58
What do the proximal convoluted tubules, the thick segments of the loops of Henle, the distal convoluted tubules and the collecting duets have in common?
They all consist of simple cuboidal epithelium ( which have microvilli and many mitochondria ) .
They actively transport molecules and ions across the wall of the nephron
59
What type of cell compose the wall of the thin segments of the ascending and descending limbs of the loop of Henle?
Simple squamous epithelium
60
What type of transport occurs on the thin segments of the ascending and descending limbs of the loop of Henle?
Diffusion of water and solutes.
61
What type of substances are permeable to the thin segments of the descending limbs of the loop of Henle?
Water
Lesser degree, solutes
62
What type of substances are permeable to the thin segments of the ascending limbs of the loop of Henle?
Solutes
# not to water!!!!!
63
Describe a general overview of the urine formation process
1. Filtration- formation of filtrate
2. Tubular reabsorption- the useful substances that enter the filtrate are reabsorbed, whereas metabolic waste products remain in the filtrate and are eliminated.
3. Tubular secretion- the active transport of solutes across the nephron walls into the filtrate.
64
What is the average percentage of the blood pumped by the heart that flows through the kidneys each minute?
21%
65
How many liters of filtrate are produced each day?
How many of it becomes urine?
Approximately 180 liters a day.
Approximately 1% or less becomes urine.
66
What is the driving force of the filtration?
Blood pressure
67
What type of process is the filtration based on?
Size filtration.
68
Explain what is size filtration
The filtration membrane allows some substances, but not others, to pass from the blood into the bowman capsule.
Water and small salutes readily pass through the openings of the filtration membrane, but blood cells and most proteins, which are too large, do not enter the bowman capsule.
69
What does the filtrate contain?
No cells and little protein (example: albumin )
70
What is the difference between the glomerular filtrate and the blood plasma?
There is Almost no plasma protein in the filtrate
71
What is the filtration pressure?
The formation of filtrate depends on a pressure gradient- called filtration pressure.
It forces fluid from the glomerular capillary across the filtration membrane into the bowman capsule.
72
What is the glomerular capillary pressure?
Glomerular hydrostatic pressure.
The blood pressure in the glomerular capillary.
This pressure is the major force causing fluid to move out from the glomerular capillary across the filtration membrane into the bowman capsule.
73
What causes the filtration pressure?
Forces that move fluid out of the glomerular capillary into the bowman capsule -minus- the forces that move fluid out of the bowman capsule and into the glomerular capillary.
74
Which forces oppose the movement of fluid into the lumen of the bowman capsule?
Capsular pressure and colloid osmotic pressure
75
Define capsular pressure
Also known as Bowman capsule pressure.
Caused by the pressure of filtrate already inside the bowman capsule.
76
Define colloid osmotic pressure
Also known as glomerular oncotic pressure.
The pressure within the glomerular capillary.
Most plasma proteins do not pass through the filtration membrane, so they produce an osmotic pressure that favors fluid movement into the glomerular capillary from the bowman capsule.
77
How can we calculate the net filtration pressure?
Glomerular capillary pressure - capsular pressure - colloid osmotic pressure = net filtration pressure
# net result or filtration pressure is positive!
# The filtration pressure has narrow range of values
78
What happens when the filtration pressure increases?
Both the filtrate volume and the urine volume increase
79
What happens when the filtration pressure decreases ?
Both the filtrate volume and the urine volume decrease
80
When does the filtration pressure increase?
When the blood pressure in glomerular capillaries increases further.
81
What happens when the filtration pressure decrease ?
When the blood pressure in the glomerular capillaries decreases.
82
What happens when the protein concentration in the blood increases?
An increase in blood protein concentration promotes the movement of water by osmosis back into the glomerular capillaries and therefore reduces the overall filtration pressure
83
What happens when the protein concentration in the blood decreases?
A decrease in blood protein concentration inhibits the movement of water by osmosis back into the glomerular capillaries, which increases the overall filtration pressure.
84
What is the healthy GFR in humans ?
Approximately 125 cm^3 / min
85
Define water potential
The tendency of water molecules to move from one region to another.
86
What determines the GFR?
The difference in water potential between the plasma in the glomerular capillaries and the filtrate in the bowman capsule.
87
What affects the water potential ?
It is lowered by the presence of solutes.
It is raised by high pressures.
88
How does the micovilli help reabsorption in the proximal tubule?
Microvilli aid to increase the surface area of Ike inner surface facing the lumen and thus increase the absorption of Na, glucose, and amino acid.
89
How does the tight junctions help reabsorption in the proximal tubule?
They are forcing fluid to pass through the cells by holding adjacent cells together (fluid cannot pass between the cells ).
90
How do the mitochondria help reabsorption in the proximal tubule?
They provide ATP for Na - K pump proteins in the outer membranes of the cells.
91
What substances pass from the proximal tubule into the interstitial fluid?
Proteins
Amino acids
Glucose
Fructose
Na +, K +, Ca, HCO3 -, Cl -
Water (osmosis)
92
Where do the substances and water go after they enter the interstitial fluid?
Peritubular capillary
93
What is the percentage of filtrate volume that is reabsorbed from the proximal convoluted tubule?.
65 %
94
How is the reabsorption of Na + occur?
The Na + -K+ pumps in the basal membranes actively more Na + ions out of the cell, and the du ions are carried away in the blood.
Thus, the concentration of Na inside of the cell is lowered and the Na ions passively diffuse into the cell from the fluid in Te lumen of the tubule.
# Na ions can only enter through special contrasporter proteins in the membrane.
95
Define cotransporter
Carrier Proteins who know how to carry two things at the same time.
96
Define secondary active transport
Active transport flat combines a pump (usually potassium- sodium ) that creates a concentration gradient for potassium in A targeted way, and so the sodium will want to enter the cell according to its concentration gradient and thus will take glucose or an amino acid on the way with it to the cell
97
What is the percentage of substances that are reabsobed At the and of the proximal convoluted tubule ?
- 100 % of glucose & amino acid
- 67 % of water, Na, K, Ca, HCO3
98
What happens to glucose once it is inside the cell?
It diffuses down its concentration gradient, through a transport protein in the basal membrane, into the blood
99
Explain the reabsorption in the loop of henle
Decreasing loop (thin)→ water is reabsorbed & some solutes move into the nephron by diffusion.
15% of the volume of the filtrate is reabsorbed and the filtrate is as concentrated as the interstitial medulla ( highly concentrated ) - passive transport.
Ascending loop (thin ) → dilutes the filtrate by removing solutes ( Na, Cl) - passive transport.
Ascending loop (thick) → actively transport Na out of the nephron, and K and CI are co transported. The thick segment is not permeable to water. As a result the highly concentrated
Filtrate is converted to a dilute solution.
100
What happens to the filtrate in the distal convoluted tubule and collecting duct?
The cuboidal cells remove water and additional solutes.
Na and Cl are reabsorbed.
19% of the original filtrate volume is reabsorbed by osmosis.
The reabsorbed water and solutes from the distal convoluted tubule enter the peritubular capillaries and the vasa recta from t collecting duct.
101
Define Deamination
The process by which an amine group ( NH2) is removed from a molecule.
102
What occurs during deamination?
The NH2 of an amino acid is removed together with additional hydrogen creating ammonia and keto acid.
Keto acid → R- CO-COOH
103
Why do we need the deamination process?
Unlike tats and carbohydrates, excess of proteins cannot be stored in the body.
But, amino acids provide useful energy, it will be wasteful to eliminate all of the excess.
Deamination help make use of this energy by removing amino groups.
104
What happens to the keto acid formed during Deamination?
It may enter the Krebs cycle and be respired, or it may be converted to glucose/ glycogen or fat for storage.
105
What happens to the ammonia formed during deamination?
NH3 is a highly soluble and highly toxic compound.
Its build up is prevented by the immediate conversion of NH3 to urea ( CO(NH2)2 ) which is less soluble and less toxic.
106
When does deamination occur ?
Liver cells
107
Define creatine
- Formed in the liver from certain amino acids.
- Most of it is used in the muscles, in the form of creatine phosphate, where it acts as an energy store.
- some of the creatine phosphate is converted by muscle metabolism to creatinine and is then excreted.
108
How is uric acid formed ?
From t break down of purines from nucleotides ( not from amino acids)
109
Whet type e of tubular secretion are there?
Active → H, K, creatinine, histamine...
Passive → NH3
110
What affects the volume and concentration of urine?
They depend on conditions in the body.
Body fluid concentration increases (above normal levels ) → The kidneys produce a small volume of concentrated urine.
This eliminates solutes and conserves water, lowers the body fluid concentration to normal.
Body fluid concentration increases (above normal levels ) → the kidneys produce a large volume of dilute urine.
Water is lost, solutes are conserved. Increase the body fluid concentration.
111
Which 3 major hormonal mechanism are involved in regulating urine concentration and volume?
1. Renine-angiotensin-aldosterone
2. Antidiuretic hormone ( ADH )
3. Atrial natriuretic hormone ( ANH )
They work together to achieve homeostasis
112
Explain the renin-angiotensin-aldosterone mechanism
Renin acts on Angiotensinogen and converts it to angiotensin 1 ( Ang1 ).
Angiotensin 1 is rapidly converted to angiotensin 2( ang2) - by angiotensin Converting enzyme ( ACE).
Angiotensin 2 acts on the adrenal cortex causing it to secrete aldosterone.
113
What is renin?
Enzyme
114
What is angiotensinogen?
Plasma protein produced by the liver.
115
What does aldosterone affect on?
1. Increases the rate of active transport of Na in the distal convoluted tubules and collecting ducts.
2. Helps Prevent further decline in blood pressure
116
How does aldosterone help to prevent a further decline in blood pressure?
when Na concentration in the filtrate is too low, the increase in aldosterone causes an increase in Na and Cl reabsorption from the nephrons, and water follows. Thus, the volume of water lost in the form of urine decreases.
117
What happens in the absence of aldosterone?
Large amounts of Na remain in the nephrons and become part of the urine → water remains in the nephron ( because of the high concentration) → increase in the urine volume.
# Cl is co transported with Na.
118
Where is ADH secreted from?
Posterior pituitary gland
119
What is vasopressin?
ADH - antidiuretic hormone
120
What is the function of ADH?
Regulates the amount of water reabsorbed by the distal convoluted tubules and collecting ducts.
ADH stops dilute urine from being produced by stimulating the reabsorption of water.
" diuresis" = the production of dilute urine.
121
Whet happens when ADH levels increase?
The permeability of the distal convoluted tubules and collecting ducts to water increases → more water is reabsorbed from the filtrate → production of small volume of concentrated urine.
122
What happens when ADH levels decrease?
The distal convoluted tubules and collecting ducts are less permeable to water → less water is reabsorbed → large volume of dilute urine is produced.
123
What regulates the release of ADH from the posterior pituitary?
The hypothalamus.
Certain cells in the hypothalamus are sensitive to changes in solute concentration.
Solute concentration in the blood increases → action potentials are sent along the axons of the ADH secreting neurons of the hypothalamus to the posterior pituitary → ADH is released.
A reduced solute concentration in the blood inhibits ADH release.
124
What are baroreceptors?
Receptors that are sensitive to changes in pressure.
They monitor blood pressure and influence ADH secretion.
Decrease in blood pressure = increase of ADH ( and vice versa )
125
Where is ANH secreted from?
From the cardiac muscle cells in the right atrium of the heart.
126
When is ANH secreted?
When the blood pressure in the right atrium increases above normal levels
127
What is the function of ANH?
ANH acts on the kidney to decrease Na reabsorption.
Na and water remain in the nephron to become urine.
The increased loss of Na and water reduces the blood volume and thus the blood pressure.
