Chapter 23: Urinary System Flashcards
Components of the Urinary System
Kidneys: filters blood, primary organ of urinary system; excrete urea and other wastes in urine (water maintenance)
Ureter: tubes leading to urinary bladder
Urinary Bladder: storage tank
Urethra: leading to outside of body (micturition)
Kidney
FUNCTIONS
- filter toxins, metabolic wastes, excess water and ions from blood
- filtrate will be formed into urine
- return any needed substances from filtrate to blood
MAIN WASTE PRODUCTS AND SOURCE
- Urea: breakdown product of amino acids
- Uric Acid: breakdown product of nucleic acids
- Creatine: breakdown product of ATP
Location of Kidney
- behind the parietal peritoneum
- superior lumbar region of posterior abdominal wall
- right kidney is crowded by liver and lies slightly inferior to the left kidney
- size=BAR OF SOAP
External Anatomy of the Kidney
- lateral surface is convex
- medial surface is concave
Hilum (Hilus) of the Kidney
- renal artery and renal vein and renal nerves enter and exit the kidney
- renal pelvis: attaches; superior expanded region of ureter
- Fibrous Capsule of dense connective tissue that adheres to the surface of the kidney
Supportive tissues of the Kidney
Renal Capsule: adheres directly to surface
- Maintains shape
- Forms barrier to prevent spread of infection
Adipose Capsule: consists of peritoneal fat
-“Peri”-around
Renal Fascia: envelope encasing capsule
Paraneal Fat: layer of fatty cushions
-“Para”-near
Renal Cortex
Superficial, granular and lighter in color
Renal Medulla
Deep, darker in color, striated (nephrons) and has cone-shaped masses (pyramids)
Renal sinus
filled space that contains renal pelvis, calices, blood vessels, and nerves
Internal Anatomical Structures of the Kidney
- renal pyramids
- renal columns
- minor calyces
- major calyces
- renal pelvis
renal pyramids
contain nephrons and urine collecting tubules
renal columns
inward extensions of renal cortex; separate adjacent pyramids
minor calyces
enclose the papillae of pyramids to collect drawing urine to empty urine into major calyces
major calyces
fusions of minor calyces to empty urine into renal pelvis
renal pelvis
flat, funnel-shaped urine collecting tube; expansion of superior ureter
Arterial Supply to Kidneys
- renal artery
- enters hilus and divides into 5 SEGMENTAL ARTERIES
- enters renal sinus and divides into LOBAR ARTERIES
- enters renal columns and divides into INTERLOBAR ARTERIES
- enters arches over medullary pyramids
- –divides into ARCUATE ARTERIES and enters pyramids
- –divides into INTERLOBULAR ARTERIES and enters cortex
Venous Return from Kidneys
- traces the pathway of arteries but in reverse
- INTERLOBULAR VEINS
- ARCUATE VEINS
- INTERLOBAR VEINS
- There are no lobar or segmental veins
- Renal Vein
Urinifeorus Tubule
“urine carrying”-anatomical structural unit of the kidney
- 2 major parts
- Nephron
- Collecting Tube
- Lined with simple epithelium
- Segments of Tubule have specific transports function
4 steps of Urine Production
- Filtration: blood filtrate leaves kidney capillaries and enters tubule lumen
- Reabsorption: ions, nutrients, water recovered from filtrate and returned to the blood via capillaries
- Secretion: any additional substances from blood that have not been included in the filtrate are moved into the tubule lumen to be included in final filtrate
- Excretion: excretion of urine from the body
Microscopic Anatomy of Kidney
- nephrons are the functional units of the kidney
- each nephron consists of a glomerulus, which is corpuscle of capillaries and a renal tubule
- the tubule forms a cup shape around the glomerulus called the glomerular capsule (Bowman’s Capsule)
- nephron structures
1. Proximal convoluted tubule
2. Loop of Henle
3. Distal Convoluted Tubule
Nephrons are associated with 2 sets of capillaries:
- Glomerular Capillary: specialized for filtration
- Allows the blood pressure in the capillary bed to be very high
- Forces fluid and solute out of the blood into the glomerular capsule - Peritubular Capillary: where most of the filtrate is reabsorbed from the renal tubules and returns to the blood
Glomerular Filtration
liquid components of the blood are filled from glomerulus into the glomerular capsule (Bowman’s Capsule)
Glomerulus is supplied by afferent arteriole and drained by efferent arteriole
3 Layers to the filtration membrane (Barrier)
- Glomerular capillaries- are leaky, fenestrated capillaries
- Water, some small solutes can cross glomerular wall
- Blood cells are larger macromolecules cannot be filtered - Podocytes: “foot cells” that cover the surface of capillaries
- Foot processes extend from them creating gaps (filtration slits or slit pores or slit diaphragms)
- Hold back some of the smaller protein - Basal laminae of endothelial cells and podocyte epithelium
Glomerular Mesangial Cell
the smooth muscle-like cell inside the glomerulus
- regulate the blood flow in the glomerulus by contracting afferent artery
- engulf macromolecules that get hung up during filtration
the nephron: glomerular filtration
- glomerular filtration is a passive process; hydrostatic pressures force the fluids and the solute through a membrane
- the glomeruli more efficient filter than other capillary beds
- filtration membrane is a large surface area and very permeable
- during filtration it is important to keep the plasma proteins in the plasma to maintain osmotic (oncotic) pressure.
- if you see blood cells or protein in the urine (protnuria) then there is a problem with the filtration membrane (common finding during diabetes and hypertension signals kidney damage. If untreated will progress to end stage renal disease and renal failure)
Tubule
Different regions of the tubule have different transport functions and permeability
- Proximal tubule: specialized for transport and it is the region where solute and water reabsorptions occurs; volume diminished
- Loop of Henle:
- —Descending limb is critical for water reabsorption
- —Ascending limb solutes are recovered
- Distal tubule: hormone-mediated regulated of uptake of solutes and water
Tubular Secretion
- similar to reabsorption
- substances such as hydrogen ion, potassium, and organic anions move from the peritubular capillary blood into the tubular lumen filtrate
- requires active transport
- tubular secretion is an important mechanism for:
1. Disposing of drugs and drug metabolites
2. Eliminating undesired substances or end products that have reabsorbed by passive process (urea and uric acid)
3. Removing exces K+
4. Controlling blood pH
Collecting Ducts
- receive urine from several different nephrons
- reabsorb and secrete ions, but their main function is to conserve body fluids
- traverse the layers of the kidney, connecting the distal tubules of nephrons
- collecting urine and sending to renal pelvis
- collecting ducts are important targets of regulatory changes in ion and water movements, including hormone-responsive pathways
transport and permeability differences in tubule regions are due to:
regional differences in the epithelia
Proximal Tubule is mainly made up of:
cubodial cells
Microscopic Anatomy of Loop of Henle
First section has caboodle, half way down descending loop transitions to squamous cells, becomes caboodle again in ascending loop
Microscopic Anatomy of Distal Tubule and Collecting Duct
Distal tubule and collecting duct has principle cells, with no microvilli. Also find intercalated cells with some microvilli
Function of the Ureters
carry urine from kidneys to urinary bladder
Cross Section of the Ureter
Several Different Layers
INNER MUCOSA LAYER, which faces lumen, and consists of transitional epithelium and stretches when ureters fill with urine
MUSCULARIS LAYER, which has inner longitudinal layer of smooth muscle and outer circular layer of smooth muscle
OUTERMOST ADVENTITIA which is made up of connective tissue
Ureters
- Ureters play an active role in urine transport, when ureters stretch stimulates muscle to contract
- Propel the urine to the bladder
- Urine is conducted from the kidneys to the urine bladder via gravity and contractions of those muscle layers in the ureters
Urinary Bladder
- Collapsible muscular sac
- Stores and expels urine
- Empty bladder will lie entirely in pelvic cavity
- Looks like inverted pyramid
- 4 corners or angles
- –2 posterolateral angles
- –Anterior angle-apex
- Has a fibrous band called the arches, which is some embryonic tissue
- –Inferior angle-neck
- Drains into urethra
- In males prostate gland lies directly below bladder
Urinary Bladder Wall
LAYERS
- Transitional Epithelium
- Lamina Propria
- Smooth Muscle
- Adventitia Connective Tissue
Transitional Epithelium
faces lumen, allows bladder to descend
Smooth Muscle
relatively thick, called depressor muscle, contractions of these muscles squeeze urine from the bladder
Urethra
thin walled tube that drains urine from the bladder to the outside of the body
External Urethral Orifice
- between outside of body and urethra
- Voluntary sphincter
- Surrounds urethra, some skeletal muscle called the urogenital diaphragm which relaxes during urination
Internal Urethral Sphincter
- junction of bladder and urethra
- involuntary sphincter of smooth muscle
- keeps urethra closed when urine is not passing through
Length of Urethra
Females: 3-4 cm
Males: 20 cm
-Prostatic urethra: passes through prostate
-Membranous Urethra: passes through urogenital diaphragm
-Spongy urethra: passes through penis
Micturition: Voiding of Urine
- Urine is formed in the renal tubules (filtrate that is not reabsorbed) and then travels through the calyxes (major and minor) until it drains into the renal pelvis
- Fluid drains from the renal pelvis into the ureter, which then leads to the urinary bladder
- The bladder stores urine until it is excreted from the body by the micturition reflex
- Micturition is initiated by a nervous reflex which causes the smooth muscle of the bladder walls to contract and then expel the urine
