What are the major components of the urinary system (excretory)?
- 2 Kidneys
- 2 Ureters
- 1 Urinary Bladder
- 1 Urethra
What are the other excretory systems?
- Digestive via Defecation
- Primary excretory organs
- Location - retroperitoneal
- Located in the lumbar region, in a depression deep in the muscles posterior to the abdomen
- Adrenal Gland found on the superior surface of the kidneys.
What is the structure of the kidneys?
Bean-shaped with a medial indention containing the hilum, where blood vessels and the ureter enter
Renal capsule - thin membranous sheath that covers the outer surface of each kidney.
What are the three layers of the renal capsule?
- Renal Fascia
- Adipose Capsule
- Fibrous Capsule
What are the internal structures of the kidney?
- Renal Pelvis
What is found within the medulla of the kindeys?
Divided into 6 - 18 cone-shaped segments called renal pyramids
Renal pyramids are where a portion of the nephrons are located
Empties urine into a calyx (channel between nephrons and renal pelvis).
Where are the nephrons found and what's their composition?
Portion located in cortex (renal corpuscle, distal/proximal tubules) and medulla (loops of henle, collecting ducts):
- 1.25 million/kidney
- 2 components:
- Glomerulus - vessels that get blood to nephron
- Tubular - urine forms in tubes
Two slightly flattened tubes found
The upper half of the ureter islocated in the abdomen and the lower half is located in the pelvic area
Move urine to the bladder through peristaltic waves every 10 - 30s.
Stretchable "bag" for urine storage
Location - posterior to pubic symphysis
Varies in size with the volume of urine it contains
Capacity - up to 600 mL.
When does the bladder send a singal to the CNS?
When the bladder contains approximately 250 mL of urine, a signal is sent to the CNS indicating the need to micturate (urinate).
What happens after the bladder sends the signal to CNS?
The sacral portions of the spinal cord, then, stimulate internal sphincter muscles to relax.
Where does urine enter the bladder and where does it release?
The ureters connect with the bladder through opening in the roof of the bladder.
Bladder drains into the urethra through a third opening in the floor of the bladder.
One tube, delivers urine from the urinary bladder to the outisde of the body.
Urethra is 3 - 4 cm long in females, 21 cm long in males.
External opening is called the urethral orifice (meatus).
Surrounded by two sphincters:
- Internal Urethral Sphincter
- External Urethral Sphincter
Where does urine formation occur?
Urine formation occurs in the nephron (located in cortex and medulla).
- Blood enters the glomerulus through the afferent arteriole
- The nephron contains several structures.
What are the four main components of the renal corpuscle?
- Afferent arteriole
- Efferent Arteriole
- Bowman's Capsule
At the glomerulus, large molecules, such as proteins, remain in the blood
Small molecules, such as glucose, water, salts, amino acids, and urea leave the blood
Bowman's Capsule (Glomerular Capsule)
A cup-like sack at the beginning of the tubular component of a nephron in the mammalian kidney that performs the first step in the filtration of blood to form urine.
Proximal Convoluted Tubule
This is the site of reabsorption into the blood (via efferent arterioles) of most of the small molecules and water (coarse reabsorption).
Excess molecules and wastes remain in the tubules.
It is here that NaCL is reabsorbed into peritubular capillaries, which allows for reabsorption of water into the capillaries.
Distal Convoluted Tubule
Absorbs molecules actively secreted from the peritubular capillaries
Molecules that move into the DCT include creatinine, uric acid, hydrogen ions, ammonia, and some drugs, such as penicillin
Fine tuning the excretory process.
Large tubule in the medulla
- Site of reabsorption of water into peritubular capillaries
- Urine is fully formed and moves from the collecting duct into the calyx, to the renal pelvis, where it drains into the ureter.
Analyzes the composition of urine to aid in determinig the health of the body
- pH - 4.6 - 8.0
- 95% water
- 5% solutes, including:
- Urochromes - pigments that give urine its yellow color (from RBC breakdown)
- Hormones - present if levels are high in the blood
What are abnormal consituents of urine?
- Blood (hematuria - blood in urine)
Hard objects formed by kidneys
- Most common - calcium stones
- Most due to insufficient fluid intake.
Can block urine flow out of kidney or can become lodged in the ureter.
- Wiat for the stone to pass (medications)
Inability to prevent discharge of urine
Stress - increased pressure causes leakage
- Sneezing, coughing laughing - especially post-childbirth in females, post-prostate removal in males
Uncontrolled contractions of destrusor muscle causes urge to urinate and urine leakage.