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Renal System - Coggle Diagram
Renal System
The Production of Urine
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TUBULAR REABSORPTION
- Substances: water, amino acids, glucose, fructose , Ca +2, CI-, HCO3-
- Proximal convoluted tubule: majority of reabsorption here; filtrate remaining in about 35%
- Active and passive mechanism of cell membrane transport
- notes the apical surface of the PCT simple cuboidal lining the nephron
- border with nephron lumen
- The basal surface borders with the interstitial fluid
- Loop of Henle: some reabsorption of water and ions. (thin & thick segments
- Thin segments: simple squamous epithelium, highly permeable to water. and some solutes can move to diffuse too
- Filtrate further reduced another (15%)
- Distal convoluted tubule and collecting duct: some reabsorption
- most of this is under control of Anti- Diuretic hormone
- ADH makes the tubule wall more permeable to water. ie more reabsorption in the presence of this hormone, therefore less and more concentrated urine
Tubular reabsorption in the PCT
- Active transport of Na+ across the basal surface- associated with the reabsorption of the most solutes
- With Na+ bring pumped out of the cell, the concentration of Na+ is low inside the cell. Therefore Na+ moves into the cell through apical surface. Other substances can move in by symport
FILTRATION
- movement of fluid, derived from blood flowing through the glomerulus, across filtration membrane
- filtrate: water, small molecules & irons that can pass through the membrane
- renal fraction: the proportion of total cardiac output that passes through the kidney
- Glomerular filtration rate(GFR): amount of filtrate produced each minute- 125ml/ minute; 180L/day
- average urine production/day: 1-2L
- most of filtrate (99%) must be reabsorbed
- removes toxins quickly from blood
The filtration membrane- remember the anatomy
- Fenestrae: the glomerular capillaries are highly permeable. Fenestrae are little windows
- Basement membrane: sandwiched between the endothelial cells of the glomerular capillaries and the podocytes
- Filtration sites: gaps between the cell processes of the podocytes
- Thus, the filtration membrane is specialised for filtration
The juxtaglomerular apparatus
- An important regulatory structure, located next to the glomerulus
- where the afferent arteriole enters the renal corpuscle, a cuff of smooth mm cells surrounds it- the juxtaglomerular cell
- A group of specialized cells at a section of the DCT- called the macular densa
- These secrete renin, important in regulation of filtrate formation and blood pressure regular ion
Filtration membrane: a filtration barrier
- Filtrate consist of: water, glucose, fructose, amino acids, urea, urate ions, creatinine, NA+, K+, Ca+2, CI-
- very little protein normally found in filtrate and urine
- Filtration is driven by pressure (blood pressure)
Filtration pressure: the force that causes filtration
- pressure gradient responsible for forcing fluid out of the
glomerular capillary across the membrane into the lumen of the Bowman capsule
TUBULAR SECREATION
- The movement of non- filtered substances, toxic by- products of metabolism, drugs or molecules not normally produced by the body, into the nephron for excretion. Occurs mainly in the distal convoluted tubule
- As with reabsorption it can be active or passive
- Ammonia is a toxic by- product of protein metabolism. Diffuses into lumen of nephron
- H+, K+ and penicillin: actively secreted into nephron
Gross anatomy of the renal system
- 2 kidneys: formation of urine
- 2 urters: passage of urine
- Urinary bladder: storage of urine
- Urethra: passage of urine
Urethra:
- Transports urine from the urinary bladder to the
outside of the body
- Transitional epithelium at the top of the urethra; the
remainder is stratified columnar
- At the junction of the urinary bladder and the urethra is
the Internal urinary sphincter
- Elastic CT and smooth muscle, prevents urine leakage
- External urinary sphincter: skeletal muscle
surrounds urethra as it extends through pelvic floor.
- We can voluntarily start/stop flow of urine
- Male urethra: extends from the inferior part of the urinary bladder through to the tip of the penis
- Female urethra: shorter; opens into vestibule anterior to vaginal opening
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Kidney
Location:
- Posterior to the parietal peritoneum, on the posterior abdominal wall, lateral to spine
- Right kidney is slightly inferior to left kidney
- Partially protected by lumbar vertebrae and ribs
- ~11cm long, ~5cm wide, ~130g
Location and gross anatomy:
- Renal capsule: connective tissue surrounding each kidney
- Adipose tissue: surrounds the outside of the capsule for protection
- Renal fascia: thin layer of connective tissue surrounds the adipose tissue; anchor kidneys to abdominal wall
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Kidney internal anatomy
- Hilum: on the concave (medial) side. Renal artery and nerves enter. Renal vein, ureter, lymphatics exit
- The hilum opens into the renal sinus, which is filled with fat and loose CT
- Kidneys are organised into two major regions
- outer cortex
- inner medulla
- Renal pyramids: bases project into cortex. Cone shaped. The base is the boundary between cortex and medulla
- Renal columns are extensions of cortical tissue into the medulla
- Apex of pyramid is renal papilla
- Papillae extend into minor calyces, which are funnel- shaped chambers
- Minor calyces funnel into larger chamber called major calyces
- Renal pelvis, a single large funnel-shaped chamber
- Renal pelvis is embedded in the renal sinus. At the hilum, it narrows, forming the ureter
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Urinary bladder:
- hollow macular container. located in pelvic cavity posterior to symphysis pubis.
- Trigone: histologically unique region. Triangular area on posterior wall, between the entry of the two utterers and the exit of the urethra
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Ureters
- passageway of urine
- From renal pelvis -> urinary bladder
- lined with transitional epithelium
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Nephron
- The functional unit of the kidney
- 4 separate regions of the nephron: renal corpuscle, proximal convoluted tubule, loop of Henle, distal convoluted tubule
- Blood enters the nephron for filtration
- Filtrate/urine is produced
- Urine flow: nephron -> papillary ducts -> minor calyces -> major calyces -> renal pelvis -> ureter
Types of nephrons
- Juxtamedullary nephrons:
- the renal corpuscle is deep in the cortex near the medulla
- Long loop of Henle extending deep into the medulla
- 15% of nephrons
- Cortical nephrons:
- Renal corpuscles located near the periphery/cortex
- Shorter loop of Henle
- 85% of nephrons
Bowman capsule
- Parietal layer:
- Outer layer. Simple squamous epithelium. Becomes cuboidal in the PCT
- Inner layer. Constructed of specialised cells called podocytes, which wrap around the glomerular capillaries
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The filtration membrane
- Fenestrae: the glomerular capillaries are highly permeable. Fenestrae are little windows
- Basement membrane: sandwiched between the endothelial cells of the glomerular capillaries and the podocytes
- Filtration slits: gaps between the cell processes of the podocytes
- Speciated for filtration
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Renal corpuscle
- The filtration portion of the nephron
- Consists of the glomerulus and the Bowman capsule
- Glomerulus:
- Network/ball of capillaries
- Bowman Capsule:
- enlarged end of the nephron, double walled chamber. Filters blood/fluid, which then enters the proximal convoluted tubule.
- Blood enters glomerulus through afferent arteriole, filtered blood exits through efferent arteriole
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