Lab 8 - Urinary System (Renal)

What organs does the urinary system consist of?

• Two ureters

• Single urinary bladder

• Single urethra

What are some functions of the urinary system?

1. Cleansing blood / ridding of waste

2. Regulation of BP

3. Regulation of pH

4. Erythropoietin release

What might a person with kidney failure experience?

• Weakness/lethargy

• Shortness of breath

• Acidosis

• Rising potassium

and much more

Where is the left kidney located? Why is the right kidney slightly lower?

• Left kidney located at the level of T12-L3

  • The right kidney is slightly lower due to displacement by the liver

What structure anchors the kidneys to the posterior abdominal wall

The renal fascia

Renal hilum

Medial entry/exit site of the kidneys

• Extends into the renal sinus

What are the semi-triangular portions of the renal medulla (inner portion) called?

Renal pyramids (pyramid of renal medulla)

What separates the renal pyramids?

Renal columns

(Also have lots of framework for blood vessels entering/exiting the cortex)

Renal papillae

• found at the ends of each renal pyramid; where calyces begin

  • Collecting ducts that transport urine to the calyces for excretion

Where is urine made?

Nephrons

Minor calyx

First stop for urine; enclose the renal papillae

• Funnel urine into the major calyx

Major calyx

Conduct urine into the renal pelvis

T/F: The kidneys have a portal system

True! Helps filter blood

What is the first vessel to enter the kidney?

Renal artery from the abdominal aorta

What are the different branches of the renal artery as you continue further into the kidneys?

1. Renal artery

2. Segmental arteries in the renal sinus

3. Interlobar arteries in the renal columns

4. Arcuate arteries between the medulla and the cortex

5. Cortical radiate arteries are in the cortex

What do the cortical radiate arteries branch into?

branch to become afferent arterioles

Where do afferent arterioles take blood?

To the glomerulus: a cluster of capillaries where filtration occurs

Directly from the glomerulus, where does blood travel?

Through efferent arterioles to the peritubular capillaries OR to the vasa recta

What happens in the peritubular capillaries?

Reabsorption and secretion

What happens in the vasa recta?

Production of concentrated urine; exchanges water and solutes

What are the three capillary beds of the kidney?

Vasa recta, peritubular capillaries, glomeruli

Blood from the peritubular capillaries and vasa recta go to the…

Cortical radiate veins

List the veins coming from the peritubular capillaries to the inferior vena cava

1. Cortical radiate v.

2. Arcuate v.

3. Interlobar v.

   1. SKIPS the segmental region

4. Renal v.

5. Inferior vena cava

Nephrons

“Functional units of the kidney”; filter blood and create urine

In the kidneys, what is filtration based on?

Size; large elements cannot pass through the filtration membrane (blood, platelets, antibodies, etc)

What are the functional regions of a nephron?

1. Renal corpuscule

2. Proximal convoluted tubule

3. Nephron loop

4. Distal convoluted tubule

What are the components of the renal corpuscle? What takes place here?

Glomerulus + capsule

• (glomerulus is inside the nephron)

Site of filtration

Filtered fluid from the glomerulus is funneled into the…

Proximal convoluted tubule (PCT)

What is the function of the proximal convoluted tubule (PCT)?

• Reabsorption of solutes (Na+, Cl-, glucose, etc.) from the blood (microvilli to increase SA)

  • Simple cuboidal

• Leaving other products in the filtrate to be disposed

*Most essential function of the nephron

Once filtrate leaves the PCT, where does it go?

Loop of Henle

The descending loop begins ___ (thick/thin), whereas the ascending loop begins (thick/thin)

Thick; thin

After the loop of Henle, where is the filtrate directed?

The distal convoluted tubule (DCT)

What processes occur in the DCT?

Reabsorption and secretion, but to a lesser extent than the PCT

Where is filtrate directed after the DCT?

Collecting ducts

What are collecting ducts?

Tubes that receive the filtrate (now mostly waste) before final modification

Where do collecting ducts empty?

Renal papilla

T/F: As urine passes through the ureters, it passively drains into the bladder

False! Urine is propelled by waves of peristalsis

Why is the bladder a highly distensible organ?

Irregular crisscrossing bands of smooth muscle (aka detrusor muscle)

• Interior is made up of transitional epithelium

What forms the trigone in the bladder?

The triangle that forms from the two ureteral openings in the bladder and the urethra

The proximal urethra is made up of _____; while the terminal portion of the urethra is made up of _____

Transitional epithelium; nonkeratinized stratified squamous epithelium

In males, there are two urinary sphincters. Describe them, and which one is present in females?

1. Internal urinary sphincters; smooth muscle + involuntary

2. External urinary sphincters; skeletal muscle + voluntary

About how long is the female urethra?

3-4 cm long from the urinary bladder to the external urethral orifice

About how long is the male urethra?

~20 cm in length from the urinary bladder to the external urethral orifice

Where does urine pass through after leaving the urinary bladder in males?

1. Prostate gland

   1. Prostatic urethra

   2. Membranous urethra

   3. Spongy (penile) urethra

Prostatic urethra

During sexual intercourse, receives sperm from the ejaculatory ducts + secretions from seminal vesicles

• also where mucus is secreted to buffer urethral pH during sex; also for lubrication for ejaculation

Why are mucus glands important in the urethra?

To protect against the extreme pH of urine

How does urine get its color?

Breakdown of RBC - irons from blood transports to urine as urochrome

What causes odor in urine?

The breakdown of urea → ammonia by bacteria

• foods (asparagus → asparagustic acid → sulfur)

How much urine do we excrete a day, roughly? What is the term for less than average urination and higher than average urination?

1-2 L /day

Oliguria

Urine output below 1-2 L/day

Anuria

No urine output

Polyuria

Urine output greater than 1-2 L / day

Glycosuria

High amounts of glucose found in urine