Module 6 Flashcards
What percentage of cardiac output do the kidneys receive when the body is at rest?
20 - 25% (1.0 - 1.25 litres blood min-1 )
. Identify two structural differences between the AFFERENT and EFFERENT arterioles?
- Lumen of the efferent arteriole is much narrower. 2. Afferent arteriole contains the granular cells Juxtaglomerular Apparatus
What are the main functions of the kidneys and the urinary system?
Excretion: Filters blood (plasma) to remove wastes & foreign substances and maintain blood volume. Helps to regulation blood ionic composition, blood pH & osmolality. Waste (urine) flows from each kidney, down its ureter to the bladder (temporarily stored)
How are KIDNEY FUNCTION and BLOOD PRESSURE HOMEOSTASIS related to each other?
Because the kidneys are able to adjust extracellular fluid volumes by varying sodium and water loss in the urine this in turn affects the plasma volume and ultimately blood volume and pressure
Identify the components of the nephron. What is the main general function of each component?
Bowman’s capsule:
PCT:
Loop of Henle
DCT:
Collecting ducts:
: Filtration
Majority of the reabsorption & secretion of solutes
Sets up salt gradient in the medulla
Some (less than PCT) reabsorption & secretion of solutes
Water reabsorption
Where are the kidneys located?
Kidneys are located between T12 and L3. The hilum of each is in line with L2. The right kidney is slightly lower due to the position of the liver.
Note: all the adipose tissue surrounding the kidney this is called the perirenal fat, what function does it serve?
It protects and supports the kidney attaching it to the posterior wall of the abdomen
Are the kidneys anterior or posterior to the parietal peritoneum?
Posterior
The kidneys are referred to as being retroperitoneal, what does this mean?
Located behind the peritoneum
What structures are found POSTERIOR to the kidneys?
Diaphragm, ribs, posterior body wall
this is the outer kidney region, which is light red and has a granular appearance. Notice the thin, transparent membrane that covers the surface of the kidney; this is the renal capsule.
Kidney cortex:
: deep to the cortex; a darker region. The medulla is segregated into triangular regions that have a striped, or striated, appearance - the medullary pyramids. The base of each pyramid faces toward the cortex; its apex, or papilla, points to the innermost kidney region.
Medullary region
areas of tissue, more like the cortex in appearance that segregate and dip downward between the pyramids
Renal columns:
medial to the hilus; a relatively flat, basin-like cavity that is continuous with the ureter, which exits from the hilus region. Finger-like extensions of the pelvis should be visible. The larger, or primary extensions are called the major calyces; subdivisions of the major calyces are the minor calyces. Note that the minor calyces terminate in cuplike areas that enclose the apices of the medullary pyramids and collect urine draining from the pyramidal tips into the pelvis.
Renal pelvis:
What structures constitute the renal corpuscle?
Glomerulus and Bowman’s Capsule
What structures contribute to the striated appearance of the medullary pyramids?
The long loops of Henle, collecting ducts and the loops of the vasa recta
Where is the juxtaglomerular apparatus located? Use a coloured pen to show its position on the diagram above:
Where the DCT meets the afferent arteriole of the nephron
What are the relative percentages of cortical & juxtamedullary nephrons in a kidney?
85% cortical; 15% juxtamedullary.
List some distinguishing features between cortical & juxtamedullary nephrons in this table:
Write down the correct sequence of tubules and ducts a drop of urine passes from its point of formation in the nephron collecting duct to be stored in the urinary bladder.
In which body cavity does the bladder lie?
Pelvic
. Into which body cavity does the bladder protrude when full?
Abdominal
The ureters enter the rear of the bladder at the posterior aspect, however their passage through the wall is not straight but at an OBLIQUE ANGLE. What is the functional reason for this?
when the bladder fills, the uretal openings are closed off by the pressure in the bladder which, prevents the backflow of urine
Fill in the following diagram
What is the trigone of the bladder?
Triangular region at the base of the bladder which lies between the openings of the two ureters and the urethra
The wall of the bladder so much thicker than that of the ureter because it contains many layers of smooth muscle. What is the name given to this thick layer of smooth muscle?
Detrusor muscle
- Identify the type of epithelium lining the inside wall of in the bladder; this is also found in the ureter. What is it designed to do?
Transitional epithelium – designed to allow expansion
Describe the urethra
The urethra is a tube carries urine from the inferior aspect of the bladder to the exterior through an opening called the external urethral orifice. The urethra is lined with pseudostratified columnar epithelium, while that near the external opening changes to stratified squamous epithelium becoming continuous with the skin.
At the site where the urethra joins the bladder is a smooth muscle sphincter called the internal urethral sphincter, which is under control and keeps the urethra closed when not in use. This sphincter is controlled by which division of the nervous system?
. There is also an external urethral sphincter, which surrounds the urethra as it passes through the pelvic floor. This sphincter is composed of skeletal muscle and is, therefore, under control. This sphincter is controlled by which division of the nervous system?
At the site where the urethra joins the bladder is a smooth muscle sphincter called the internal urethral sphincter, which is under involuntary control and keeps the urethra closed when not in use. This sphincter is controlled by which division of the nervous system? __Autonomic___________. There is also an external urethral sphincter, which surrounds the urethra as it passes through the pelvic floor. This sphincter is composed of skeletal muscle and is, therefore, under voluntary control. This sphincter is controlled by which division of the nervous system? ___Somatic Motor_________.
Observe the differences between the male and female urethra. Identify two main differences between male and female urethras.
In the male the urethra is a shared duct of both the urinary and reproductive systems. Male has associated reproductive glands. Two different ducts in female
What type of muscle are somatic motor nerves innervating?
Skeletal
What larger structure is this sphincter a part of?
Pelvic Floor
What is the function of afferent Pathway 2?
Sensory: signals increased stretch on bladder wall when full
Name the two factors that determine which plasma components will pass across the membrane
Size and charge
List some plasma components that pass through the filtration membrane.
Glucose, water, small fats, amino acids, urea, Na+ , Cl
What type of capillaries are the glomerular capillaries? Why would this type of capillary be necessary in this location?
Fenestrated; Pores for filtering
What are podocytes and what do they contribute to the filtration membrane?
Create filtration slits-pores; cells with foot processes that create slits
What three pressures are responsible for creating the net forces which control glomerular filtration? Briefly describe how each one of these pressures is created.
GCP = Glomerular Capillary Pressure (blood pressure in the glomerulus); 2. BCOP = Blood Colloidal Osmotic Pressure (osmotic pressure from proteins in plasma); 3. CHP = Capsular Hydrostatic Pressure (resistance pressure caused by pushing filtrate
Glomerular filtration is largely dependent on the body’s blood pressure. What is the process called which allows the kidneys to protect themselves from normal fluctuations in blood pressure?
Autoregulation
This process ultimately bring about a change in afferent arteriole diameter; how can this affect glomerular filtration?
An increase the diameter of the afferent arteriole increases the blood flow to the glomerulus and therefore pressure in the glomerulus, increasing GFR & vice versa.
In an emergency, the kidneys deliberately and quickly change glomerular filtration to maintain blood pressure homeostasis? What division of the nervous system is involved?
Sympathetic Nervous System
Where in the adrenal gland is aldosterone produced?
Where in the kidney does aldosterone exert its action?
What effect does aldosterone secretion have on blood volume and therefore, blood pressure?
Increases both
What are the actions of angiotensin II?
- It is the primary stimulus for secretion of ALDOSTERONE, which increases Na+ reabsorption in the DCT & CD by stimulating the synthesis of new protein in the kidney principal cells (in the wall of the DCT and CD). 2. A powerful vasoconstrictor to increase blood pressure. 3. It stimulates thirst and ADH release by the posterior pituitary gland (for water retention)
What occurs in the Absence of ADH?
The collecting ducts are impermeable to water movement; no reabsorption occurs. This mechanism allows for a significant loss of body water during hydrated states.
What occurs in the Presence of ADH?
A significant amount of water reabsorption occurs, with the kidneys forming a very concentrated urine. This is a fast reaction as it occurs within 5-10 min of ADH secretion. Water passes from cell to interstitium/vasa recta due to the high OP gradient established by the Loops of Henle. It is possible to concentrate the urine up to 1200 mOsm L-1 (maximum osmolality of the salt gradient) as the filtrate moves through the inner medulla. The reabsorbed water is collected by the vasa recta and returned to the general circulation.
Hypothalamic sensors that monitor plasma osmolality are called?
Osmoreceptors
From which endocrine gland is ADH released into the blood; be specific?
Posterior pituitary gland
Where in the kidney does ADH exert its action?
DCT and Collecting ducts
How does ADH work at it target cells? (hint: is it a peptide or lipid hormone)
ADH is a peptide hormone and therefore binds to a receptor on the outside of the target cell which activates a 2nd messenger (cAMP) to initiate its response.
Would ADH secretion increase if a person was dehydrated? (yes or no)
Yes
Would ADH secretion increase if a person suffered from a haemorrhage? (yes or no)
Yes
How does ADH secretion affect urine volume?
In presence of ADH urine volume is reduced and more concentrated
Can you suggest why ADH is also known as vasopressin?
It is a powerful vasoconstrictor substance
