A&PII Ch.24 Urinary System Anatomy Flashcards
What are the 4 components of the Urinary Sytem and their functions?
- Kidneys (filter blood, remove waste products, convert filtrate to urine)
- Ureters (transport urine from kidneys to urinary bladder)
- Bladder (expandable muscular sac that stores up to 1L of urine)
*Urethra (eliminates urine from the body)
Processes that occur as filtrate is converted to urine
- Elimination of metabolic wastes
- Regulation of ion levels (Na+, K+, Ca2+)
- Regulation of acid-base balance (alters levels of H+ and HCO3- (bicarbonate))
- Regulation of blood pressure
*Elimination of biologically active molecules (hormones, drugs)
What are some other functions of the kidney?
- Formation of calcitriol
- Production and release of erythropoietin (EPO) (secretes EPO in response to low blood oxygen)
-stimulates red bone marrow to increase erythrocyte production - Potential to engage in gluconeogenesis (prolonged fasting or starvation, occurs in kidney cortex)
-produces glucose from noncarbohydrate sources; maintain glucose levels
Features of the Kidneys
- two symmetrical, bean-shaped organs
- size of hand to second knuckle
- Concave medial border, hilum (where vessels, nerves, ureter connect to kidney
- Lateral border convex
- Adrenal gland rests on superior aspect of kidney
More features of the Kidneys
- located in the retroperitoneal space (posterior to the peritoneum)
- extend from T12 to L3
- protected posteriorly by the floating ribs
- anchored by various layers of connective tissue
What are the three connective tissue layers that Encapsulate the Kidneys?
- Renal Fascia
-most superficial layer
-dense irregular connective tissue
-Surrounds both kidneys and the adrenal glands - Perinephric/ Perirenal Fat Capsule
-layer of adipose tissue= cushioning effect - Renal Capsule
-directly covers the outer surface of the kidney
-dense irregular CT, helps prevent trauma and pathogen penetration
Internal Kidney Features
- Renal Cortex: outer regions (granular and reddish- brown
- Renal Medulla: inner regions (composed of renal pyramids with striped appearance)
- Renal Pyramids: clusters of many nephrons and collecting ducts
- Major and Minor Calyxes: collect urine from renal lobes (a pyramid and surrounding cortical tissue
What are the features of the Cortex and Medulla?
- the cortex is the outer portion of the kidney where the filtration of blood occurs
- the medulla houses most of the nephron tubule space, where urine forms and is concentrated
What are the connective tissue layers surrounding the kidney from outside to inside?
Renal Fascia-> Perirenal fat capsule-> Renal Capsule
What structures collect urine from renal pyramids?
Minor and Major calyxes
Features of the ureters
- Carry urine out of the kidneys to the bladder
- Capable of peristalsis
- Connect to the bladder at an angle that prevents backflow of urine
- Further bladder filling also compresses the distal end of the ureter, further preventing backflow
Microscopic features of the ureters
- Deepest Layer (Mucosal)
-Transitional Epithelium
-Readily stretches to accommodate distension from urine filling - Middle Layer (Muscularis)
- senses distension with urine filling and triggers reflexive peristalsis
- Superficial layer (Adventitia)
-Fibrous Connective tissue
-anchors the ureter in place
Common features of the bladder found in men and women
- Inner mucosa of bladder: transitional epithelium
- Middle layer (detrusor): contains muscle that contracts to drive urination
- Thick muscle near the urethra forms the internal urethral sphincter
- Epithelium transitions to stratified squamous epithelium near the urethra’s opening to the outside
- Passes through a ring of skeletal muscle on its way out (external urethral sphincter)
Female v.s Male urinary system includes..
- MALE: Urethra is longer than 20cm and functions for transport of both urine and semen
*FEMALE: Urethra is only 3-5cm in length; functions only in transport of urine
Kidney Vasculature Features
- Renal artery enters at the hilum
- Branches into several segmental arteries, which branch into interlobar arteries
- Interlobar arteries travel through the renal columns and branch into arcuate arteries in the cortex
- These branch into cortical radiate arteries (interlobular), then microscopic afferent arterioles
Structure of Kidney Nephrons
- Nephrons are the structural and functional unit of urine formation in the kidney
- Afferent arterioles drain into the glomerulus
- Filtration occurs when fluid and solutes are forced from the blood in the glomerulus into the space in the surrounding Bowman’s capsule
*Blood is drained from the glomerulus by efferent arterioles
What is the flow of fluid through the nephron’s tubules?
- Proximal Convoluted Tubule (PCT)
-located entirely within the cortex
-simple cuboidal epithelium with microvilli - Descending Tubule (DT)
-descends into the medulla
-alternates between thick and thin segments - Loop of Henle (LH)
-connects ascending and descending tubes - Ascending Tube (AT)
-alternates between thick and thin segments - Distal Convoluted Tubule (DCT)
-simple cuboidal epithelium WITHOUT microvilli
Nephrons types and classification
- Two types are Cortical and Juxtamedullary
- Classified based on two factors of relative position of renal corpuscle in the cortex and the length of the nephron loop
Cortical Nephrons
- Oriented with renal corpuscles near peripheral cortex
- Short nephron loop barely penetrates medulla
- 85% of nephrons
- Main function is for solute reabsorption and excretion
Juxtamedullary Nephrons
- 15% of nephrons
- Long nephron loop extended deep to the medulla
- main function is to concentrate urine
Collecting Tubules and Collecting Ducts
*Nephrons drain into a collecting tubule
*Multiple collecting tubules empty into larger collecting ducts
* Numerous collecting ducts empty into papillary duct located within renal papilla
*Specialized Epithelial Cells (in CT, CD)
* Principal Cells responsive to hormones aldosterone and antidiuretic hormone (ADH)
*Intercalated Cells specialized epithelial cells help regulate urine pH and blood pH
Flow of fluid after filtration through the nephron
- Filtrate from many Nephrons into the Collecting Duct (CD)
- Fluid flows from CD through either Principal Cells (adjust urine to maintain the body’s water, Na+, and K+ balance) or Intercalated Cells (responsible for acid-base balance)
- From the Principal or Intercalated Cells fluid then flows into the papillary duct
Features of the Juxtaglomerular Apparatus (JGA)
*occurs when a portion of the DCT comes into contact with the afferent arteriole
* Macula Densa cells in DCT monitor the concentrations of Cl- and Na+ in filtrate
* Granular (a.k.a juxtaglomerular) cells respond to changes in blood pressure in the afferent arteriole
Juxtaglomerular Apparatus
- JG apparatus helps regulate blood filtrate formation, systemic blood pressure
- Components of the JG apparatus include
Granular Cells and Macula Densa
Granular Cells of afferent arteriole
- component of JG apparatus
*modified smooth muscle cells of afferent arteriole - located near entrance to renal corpuscle
- contract when stimulated by stretch or sympathetic stimulation
- synthesize, store, and release renin
Macula Densa Cells of DCT
- component of JG apparatus
- modified epithelial cells in wall of DCT
- located on tubule side next to afferent arteriole
- detect changes in NaCl concentration of fluid in lumen of DCT
- signal granular cells to release renin through paracrine stimulation
Human Fluid Pools
- The human body is composed of three interconnected pools:
-intracellular fluid (inside cells)
-intravascular fluid (inside blood vessels)
-interstitial fluid (between cells) - Extracellular= Interstitial + Intervascular
Fluid Pool Solute Profiles are not identical
- Intracellular Fluid (ICF)
-water, electrolytes, small molecules, non-electrolytes, proteins
-20% to 30% protein, pH 7.00 - K+ most common
- Extracellular Fluid (ECF)
-far less protein, electrolytes
-pH 7.40
-Na+ most common
Thirst is generated by..
- Exercise, eating salty food, dry mouth
- A 1% to 2% increase in osmolarity
-osmolarity- solutes/ L, expressed as osmoles/liter
-0.290 to 0.295 Osm/L - Blood loss
- Release of antidiuretic hormone (ADH)
- thirst is quenched as soon as water contacts the osmolarity receptors in our cheeks- this happens to prevent over-consumption of water
Water loss occurs in what various ways?
- Kidneys (60%)
- Lungs (28%)- breathing out evaporated water
- Sweat (8% or more)- depends on external temperature, humidity, and activity level
- Feces (4%)
What clinical disorders can arise from too much or too little water?
Dehydration, Hypotonic Hydration (rare), Hypovolemia, Hypervolemia
Dehydration
- excessive water loss via sweating, diarrhea, vomiting, and little water ingestion
- clinical symptoms include sticky oral mucosa, dry flushed skin, reduced urine formation, thirst, weight loss, fever, CNS abnormalities and death
Hypotonic Hydration
- Rare ingestion of too much water
- decrease in fluid pool osmolarity
- CNS dysfunction
Hypovolemia
- loss of plasma volume
- loss of water and solutes
- Diabetes, burns, wounds, diarrhea, vomiting
Hypervolemia
- too much plasma volume
- renal or liver failure
Which nephron’s major function is to concentrate urine?
juxtamedullary nephrons
Principal and intercalated cells can be found where?
Collecting tubules and collecting ducts
