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BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE > ANAPHY LEC > Flashcards

ANAPHY LEC Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

What is the Urinary System?

A
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2
Q

What are the Organs of the Urinary System?

A

Kidneys
Ureters
Urinary Bladder
Urethra

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3
Q

Location and Dimension of the Kidneys.

A

Dimensions
Reddish-brown, bean shaped
12cm long, 6cm wide, 3cm thick

High on posterior abdominal wall
at the level of T12 to L3- superior lumbar region

Retroperitoneal & against the dorsal body wall

The right kidney is slightly lower than the left, convex laterally

Attached to ureters, renal blood vessels, and nerves at renal hilus (medial indention)

Atop each kidney is an adrenal gland

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4
Q

What is the Adipose Capsule?

A

Surrounds the kidney
Provides protection to the kidney
Helps keep the kidney in its correct location against muscles of posterior trunk wall
Ptosis-kidneys drop to a lower position due to rapid fat loss, creating problems with the ureters.
Ptosis can lead to hydronephrosis, a condition where urine backs up the ureters and exerts pressure on the kidney tissue.

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5
Q

What is the Renal Capsule?

A

Surrounds each kidney

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6
Q

What is the Renal Cortex?

A

outer forms an outer shell

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7
Q

What are Renal Columns?

A

extensions of cortex material inward

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8
Q

What is the Renal medulla?

A

inside the cortex, contains medullary (renal) pyramids

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9
Q

What are the Medullary Pyramids?

A

triangular regions of tissue in the medulla, appear striated

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10
Q

What is the Renal Pelvis?

A

inner collecting tube, divides into major and minor calyces.

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11
Q

What are Calyces?

A

cup-shaped structures enclosing the tips of the pyramids that collect and funnel urine towards the renal pelvis

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12
Q

What are the functions of the Urinary System?

A

Elimination of waste products
filtering gallons of fluid from the bloodstream every day creating “filtrate”
“filtrate” includes: metabolic wastes, ionic salts, toxins, drugs

Maintenance of the circulation
Red blood cell production- by producing hormone erythropoietin to stimulate RBC production in bone marrow
Blood pressure (vessel size)- by producing renin which causes vasoconstriction
Blood volume (water balance)- ADH released from Anterior Pituitary targets the kidney to limit water loss when blood pressure decreases or changes in blood composition

Blood composition (electrolyte balance)- water follows salt; aldosterone reclaims sodium to the blood
Blood pH- regulates H+ ions and HCO3- ions

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13
Q

Blood Flow in the Kidneys

A

Rich blood supply to filter blood and adjust blood composition
~¼ of blood supply passes through the kidneys each minute
Blood enters the kidneys under extremely high pressure
Renal artery arises from abdominal aorta, divides into Segmental artery at hilus

Inside renal pelvis, Segmental artery divides into Lobar artery, which branch into Interlobar artery travelling thru the renal column to reach the renal cortex
At the medulla-cortex junction, the Interlobar artery curves over the medullary pyramids as the Arcuate artery.
Small Interlobular arterioles branch off of the Arcuate artery and move away from the renal cortex and into the Nephron of the kidney

The final branches of the interlobular arteries are called afferent arterioles.
Afferent arterioles lead to the glomerulus, a network of capillaries that are involved in filtration.
Leading away from the glomerulus, blood less filtrate travels through the efferent arterioles and into the peritubular capillaries.
From there, blood moves through similar veins that parallel the arteries at their respective locations.

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14
Q

In simple terms, illustrate the blood flow in the kidneys.

A

Aorta - Renal Artery - Segmental Artery - Lobar Artery - Interlobar Artery - Arcuate Artery - Interlobular Artery - Afferent Arteriole - Glomerulus Capillaries - Efferent Arteriole - Peritubular capillaries - Interlobular vein - Arcuate vein - Interlobar vein - Renal vein - Inferior Vena Cava

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15
Q

What is a Nephron?

A

The structural and functional units of the kidneys
Over 1 million
Responsible for forming urine
Consist of renal corpuscle and renal tubule
Renal corpuscle composed of a knot of capillaries called the Glomerulus (a.k.a. Bowman’s Capsule)
Renal tubule- enlarged, closed, cup-shaped end giving rise to the PCT, dLOH, aLOH, DCT, and CD.

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16
Q

What is the Glomerulus?

A

A specialized capillary bed fed and drained by arterioles.

Glomerular capillaries filter fluid from the blood into the renal tubule

Capillaries attached to arterioles on both sides in order to maintain high pressure

Large afferent arteriole-arises from interlobular artery (feeder vessel); large in diameter, high resistance vessels that force fluid & solutes (filtrate) out of the blood into the glomerular capsule.

Narrow efferent arteriole-merges to become the interlobular vein; draining vessel.

Glomerular capillaries are covered with podocytes from the inner (visceral) layer of the glomerular capsule.

Podocytes have long, branching processes called pedicles that intertwine with one another and cling to the glomerular capillaries.

Filtration slits between the pedicles form a porous membrane around the glomerular capillaries.

The glomerular capillaries sit within a glomerular capsule (Bowman’s capsule)

Expansion of renal tubule

Receives filtered fluid

Renal tubule coils into the PCT, then the dLOH, aLOH, DCT and finally, the CD.

Along the PCT, much of the filtrate is reclaimed

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17
Q

What is the Renal Tubule?

A

Glomerular (Bowman’s) capsule enlarged beginning of renal tubule

Proximal convoluted tubule- lumen surface (surface exposed to filtrate) is covered with dense microvilli to increase surface area.

The descending limb of the nephron - Loop of Henle

The ascending limb of the nephron coils tightly again into the distal convoluted tubule

Many DCT’s merge in renal cortex to form a collecting duct

Collecting ducts not a part of nephron

Collecting ducts receive urine from nephrons and deliver it to the major calyx and renal pelvis.

CD run downward through the medullary pyramids, giving them their striped appearance.

18
Q

How does the blood supply work inside a Nephron?

A

Peritubular capillary

Efferent arteriole braches into a second capillary bed

Blood under low pressure

Capillaries adapted for reabsorption instead of filtration.

Attached to a venule and eventually lead to the interlobular veins to drain blood from the glomerulus

Cling close to the renal tubule where they receive solutes and water from the renal tubule cells as these substances from the filtrate are reabsorbed into the blood.

Juxtaglomerular apparatus

At origin of the DCT it contacts afferent and efferent arterioles

Epithelial cells of DCT narrow and densely packed, called macula densa

Together with smooth muscle cells, comprise the juxtaglomerular apparatus

Control renin secretion & indirectly, aldosterone secretion

19
Q

What are the types of Nephrons?

A

Cortical nephrons
Located entirely in the cortex
Includes most nephrons

Juxtamedullary nephrons
Found at the boundary of the cortex and medulla and their LOH dip deep into the medulla.

20
Q

What are the Urine Formation Processes?

A

Filtration - Water & solutes smaller than proteins are forced through the capillary walls and pores (of the glomerulus) into the renal tubule (Bowman’s capsule).

Reabsorption - Water, glucose, amino acids & needed ions are transported out of the filtrate into the peritubular capillary cells and then enter the capillary blood.

Secretion - Hydrogen ions, Potassium ions, creatinine & drugs are removed from the peritubular capillaries (blood) and secreted by the peritubular capillary cells into the filtrate.

21
Q

How does Filtration work in the urine formation process?

A

Beginning step of urine formation

Occurs at the glomerulus, nonselective passive process

Water and solutes smaller than proteins are forced through capillary walls of the glomerulus, which act as a filter.

Fenestrations – (openings in glomerular walls) make glomerulus more permeable than other arterioles.

Podocytes cover capillaries, make membrane impermeable to plasma proteins.

Blood cells cannot pass out to the capillaries; filtrate is essentially blood plasma w/o blood proteins, blood cells.

Filtrate is collected in the glomerular (Bowman’s) capsule and leaves via the renal tubule

22
Q

What is Filtration Pressure?

A

Hydrostatic pressure of blood forces substances through capillary wall.

Net filtration pressure normally always positive

Hydrostatic pressure of blood is greater than the hydrostatic pressure of the glomerulus capsule and the osmotic pressure of glomerulus plasma

If arterial blood pressure falls dramatically, the glomerular hydrostatic pressure falls below level needed for filtration.

The epithelial cells of renal tubules lack nutrients and cells die. Can lead to renal failure.

23
Q

What is the Filtration rate?

A

Rate of filtration is directly proportional to net filtration pressure.

Regulation of filtration rate

Rate typically constant; may need to increase or decrease to maintain homeostasis

  1. Sympathetic nervous system reflexes
    Respond to drops in blood pressure and blood volume
    As pressure drops, sympathetic nerves cause vasoconstriction of afferent arterioles.
    Decreases rate of filtration
    Less urine produced, water is conserved
    As pressure rises, sympathetic nerves cause vasoconstriction of efferent arterioles.
    Increases rate of filtration
    More urine produced, water is removed
  2. Renin production by JGA
    Renin is an enzyme controlling filtration rate
    Juxtaglomerular cells secrete renin in response to 3 stimuli
    Sympathetic stimulation (fast response)
    Specialized pressure receptors in afferent arterioles sense decrease in blood pressure
    Macula densa senses decrease in chloride, potassium, and sodium ions reaching distal tubule

Released renin reacts with angiotensinogen in bloodstream to form angiotensin I  which is converted into angiotensin II by the angiotensin I converting enzyme, ACE

Angiotensin II acts to vasoconstrict efferent arteriole

Blood backs up into glomerulus, increasing pressure and maintains filtration rate

Angiotension II also stimulates secretion of aldosterone from adrenal glands

Stimulates tubular reabsorption of sodium & H2O follows

24
Q

What is Reabsorption?

A

The composition of urine is different than the composition of glomerular filtrate.

Tubular reabsorption returns substances to the internal environment of the blood by moving substances through the renal tubule walls into the peritubular capillaries (99%)

Some water, ions, glucose, amino acids
Some reabsorption is passive
= water  osmosis
= small ions diffusion

Most is active using protein carriers  by active transport

Most reabsorption occurs in the proximal convoluted tubule, where microvilli cells act as transporters, taking up needed substances from the filtrate and absorbing them into the peritubular capillary blood.

Substances that remain in the renal tubule become more concentrated as water is reabsorbed from the filtrate.

25
Q

How does the reabsorption of Sodium and water works?

A

The sodium potassium pump reabsorbs 70% of sodium ions in the PCT.

The positive sodium ions attract negative ions across the membrane as well

Water reabsorption occurs passively across the membrane to areas of high solute concentration

Therefore, more sodium reabsorption = more water reabsorption

Active transport of sodium ions occurs along remainder of nephron and collecting duct

Almost all sodium ions and water are reabsorbed.

26
Q

What are the materials that are not reabsorbed?

A

Nitrogenous waste products

Urea – formed by liver; end product of protein breakdown when amino acids are used to produce energy

Uric acid – released when nucleic acids are metabolized

Creatinine – associated with creatine metabolism in muscle tissue

Excess water

27
Q

What is secretion?

A

Some materials move from the peritubular capillaries into the renal tubules to be eliminated in urine.

E.g.:
Hydrogen ions; potassium ions
Creatinine
Drugs; penicillin; histamine

Process is important for getting rid of substances not already in the filtrate or for controlling pH.

Materials left in the renal tubule move toward the ureter

28
Q

Summarize the Urine Formation.

A

Glomerular filtration of materials from blood plasma

Reabsorption of substances, including glucose; water, sodium

Secretion of substances, including penicillin, histamine, hydrogen and potassium ions

29
Q

Water Balance: What is the normal amount of water in the human body?

A

Infant - 70%
Adult Male - 60%
Adult Female - 50%
Senior Citizen - 50%

Water is necessary for many body functions and levels must be maintained.

30
Q

What happens to water and salt in the body?

A

Changes in electrolyte balance causes water to move from one compartment to another

Alters blood volume and blood pressure (think of aldosterone)

Can impair the activity of cells (swelling/edema)

Water intake must equal water output

Sources for water intake/output:

Intake: Ingested foods and fluids, Water produced from metabolic processes (glycolysis)

Output: Vaporization out of the lungs, Lost in perspiration, Leaves the body in the feces, Urine production

31
Q

Diluted vs. Concentrated Urine

A

Diluted urine is produced if water intake is excessive

Less urine (concentrated) is produced if large amounts of water are lost

Proper concentrations of various electrolytes must be present

32
Q

Regulation of Water and Electrolyte Reabsorption

A

Regulation is primarily by hormones

33
Q

What is the purpose of Antidiuretic hormone (ADH)?

A

prevents excessive water loss in urine

Neurons in the hypothalamus produce ADH, which are released by the anterior pituitary gland in response to a decrease in blood volume or water concentration

ADH increases the water permeability of the distal convoluted tubule epithelium to the peritubular capillaries

Decreases volume of urine, increasing concentration of solutes

Negative feedback control

34
Q

What is the purpose of Aldosterone?

A

regulates sodium ion content of extracellular fluid

Triggered by the renin-angiotensin mechanism

Stimulates the DCT to reabsorb sodium and excrete potassium

35
Q

Acid-Base Balance in Blood

A

Blood pH must remain between 7.35 and 7.45 to maintain homeostasis

Alkalosis – pH above 7.45
Acidosis – pH below 7.35

Most acid-base balance is maintained by the kidneys

Excrete bicarbonate ions if needed

Conserve / generate new bicarbonate ions if needed

Excrete hydrogen ions if needed

Conserve / generate new hydrogen ions if needed

36
Q

Urine composition

A

Composition differs considerably based upon diet, metabolic activity, urine output.

~95% water, contains urea and uric acid, electrolytes and amino acids (trace amount)

Volume produced ranges from 0.6-2.5 liters per day (1.8L average).

Depends on fluid intake, body and ambient air temperature, humidity, respiratory rate, emotional state

Output of 50-60ml per hour normal, less than 30ml per hour may indicate kidney failure

37
Q

What are Ureters?

A

Slender tubes attaching the kidney to the bladder 10-12” long & ¼” diameter

Superior end is continuous with the renal pelvis of the kidney

Mucosal lining is continuous with that lining the renal pelvis and the bladder below.

Enter the posterior aspect of the bladder at a slight angle

Runs behind the peritoneum

Peristalsis aids gravity in urine transport from the kidneys to the bladder.

Smooth muscle layers in the ureter walls contract to propel urine.

There is a valve-like fold of bladder mucosa that flap over the ureter openings to prevent backflow.

Renal calculi= calculus means little stone; result of precipitated uric acid salts created by bacterial infections, urinary retention, and alkaline urine. Lithotripsy or surgery are common treatments.

38
Q

Urinary Bladder

A

Smooth, collapsible, muscular sac

Temporarily stores urine

Located retroperitoneally in the pelvis posterior to the pubic symphysis.

Trigone – three openings

Two from the ureters (ureteral orifices)

One to the urethra (internal urethral orifice) which drains the bladder.

Common site for bacterial infections

In males, prostate gland surrounds the neck of the bladder where it empties into the urethra.

39
Q

Urinary Bladder Wall

A

Three layers of smooth muscle (detrusor muscle)

Mucosa made of transitional epithelium

Walls are thick and folded in an empty bladder 2-3” long

Bladder can expand significantly without increasing internal pressure

As it fills, the bladder rises superiorly in the abdominal cavity becoming firm and pear shaped.

A moderately full bladder can hold ~500mL (1 pint) of urine.

A full bladder can stretch to hold more than twice that amount.

40
Q

Urethra

A

Thin-walled tube that carries urine from the bladder to the outside of the body by peristalsis

Release of urine is controlled by two sphincters

Internal urethral sphincter (involuntary) – a thickening of smooth muscle at the bladder-urethra jxn. keeps urethra closed when urine is not being passed.

External urethral sphincter (voluntary) – skeletal muscle that controls urine as the urethra passes through the pelvic floor.

41
Q

Urethra Gender Differences

A

Male:
- Ureter
- Smooth muscle
- Ureteral Opening
- Prostate Gland
- Internal sphincter
- External sphincter
- Urethra

Female:
- Ureter
- Smooth muscle
- Ureteral opening
- Internal sphincter
- External sphincter
- Urethra

Length
Females – 3–4 cm (1-1.5 inches)
Males – 20 cm (7-8 inches)

Location
Females – along wall of the vagina
Males – through the prostate and penis

Function
Females – only carries urine
Males – carries urine and is a passageway for sperm cells

Males:
Prostatic, membranous and spongy (penile) urethrae
Enlargement of the prostate gland causes urinary retention
can be corrected with a catheter

Females:
Feces can enter urethral opening causing
Uretritis-inflammation of the urethra
Pyelitis or pyelonephritis-inflammation of the kidneys
Urinary tract infections-bacterial infection
Dysuria
Urgency
Frequency
Fever
Cloudy urine
Bloody urine

42
Q

Micturition (Voiding)

A

Both sphincter muscles must open to allow voiding

The internal urethral sphincter is relaxed after stretching of the bladder ~200mL

Activation is from an impulse sent to the spinal cord and then back via the pelvic nerves

The external urethral sphincter must be voluntarily relaxed

Incontinence-inability to control micturition

Retention-inability to micturate

BACHELOR OF SCIENCE IN MEDICAL LABORATORY SCIENCE (15 decks)

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