Physiology 1021 Study Guide - Midterm Guide: Adrenal Gland, Homeostasis, Aquaporin 2

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RENAL
Kidneys have 7 major functions:
- Regulation of extracellular fluid volume and blood pressure
- Regulation of osmolarity
- Maintenance of ion balance
- Maintenance of body pH
- Excretion of wastes
- Production of hormones
- Gluconeogenesis (produces more glucose from non-carb sources)
Kidney Anatomy
- We have 2 bean shaped kidneys
- Located posteriorly to abdomen - 1 on each side of spine
- They are positioned retroperitoneal - sandwiched between the membranes that line the
abdomen and the bones/muscles of the back.
- Inner concave side of kidney is where the blood supply enters and exits (via renal artery
+ vein)
- Removal of urine produced by kidney exits by ureter - also located at the same location
as kidney
Major Anatomical Features of Kidney
- Major calyces are large funnel shaped structures that collect processed fluid from minor
calyces
- Minor calyces fit over major calyces like pyramid shaped segments of filtering units
- These calyces are in the inner portion of the kidney, this tissue is called “medulla”
- The calyces are organized radially around renal pelvis
- The innermost hollow centre of the kidney is where the urine collects
- The cortex is the outermost tissue of kidney, it lies on top of the medulla
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- And “nephrons” are the filtering units of kidney, they’re found throughout the medulla and
cortex + intertwined with blood vessels.
The Nephron
- The nephron is the functional unit of the kidney.
- Each kidney has about one million of these.
- It is made up of two basic structures: renal corpuscle and the tubule
- The outside of renal corpuscle is called “bowman’s capsule” and the inside is a
specialized capillary bed called “glomerulus”
- Renal corpuscle: where blood filtration occurs
- Tubule: where the filtered fluid is processed
- The tubule is a tube like structure made up of a single layer of epithelial cells.
Parts of a Nephron
<-- minor calyces → major calyces →
renal pelvis → urine out
Cortical and Juxtamedullary Nephrons
- There are 2 main types of nephrons based on their position within the two layers of the
kidney; cortical and juxtamedullary.
- Humans have many more cortical than juxtamedullary. The ratio does vary in species.
- The more juxtamedullary nephrons someone has, the better they can concentrate their
urine and reserve water in the body.
- Both function to filter blood to produce the ultrafiltrate.
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- There are many key anatomical differences in and around the loop of henle - between
these two types of nephrons.
Differences between the 2 nephron types
- Location of the corpuscle
- Length of the loop of henle
- Anatomy of the capillary bed that surrounds the tubule
Renal Corpuscle
- Part of the nephron that filters blood and produces a fluid called ultrafiltrate.
- Its found in the cortex of the kidney, thus it has a granular appearance.
- Its made up of two structures: bowman’s capsule and glomerulus.
Bowman’s capsule
- Fluid filled hollow ball like structure that surrounds glomerulus.
- The capsule is continuous with the beginning of the first part of the tubule → proximal
tubule.
- And the cells outside of the capsule are called “simple squamous epithelial cells”
- The part of the capsule that physically contact the glomerulus is a specialized type of
epithelial cells called “podocytes”.
Juxtaglomerular apparatus (JGA)
- Composed of the function of a part of the tubule that is called the late ascending limb of
loop of henle.
- This passes in between 2 blood vessels that enter and exit the corpuscle called the
efferent and afferent arterioles.
- Specialized cells in the late ascending limb of loop of henle are called “macula densa
cells”
- These cells can detect the concentration of sodium and chloride in the ultrafiltrate as it
passes through the tubule.
- Cells beside macula densa are called the juxtaglomerular cells (granular cells) that are
responsible for producing + releasing the enzyme “renin”.
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Document Summary

Regulation of extracellular fluid volume and blood pressure. Gluconeogenesis (produces more glucose from non-carb sources) Located posteriorly to abdomen - 1 on each side of spine. They are positioned retroperitoneal - sandwiched between the membranes that line the abdomen and the bones/muscles of the back. Inner concave side of kidney is where the blood supply enters and exits (via renal artery. Removal of urine produced by kidney exits by ureter - also located at the same location as kidney. Major calyces are large funnel shaped structures that collect processed fluid from minor calyces. Minor calyces fit over major calyces like pyramid shaped segments of filtering units. These calyces are in the inner portion of the kidney, this tissue is called medulla . The calyces are organized radially around renal pelvis. The innermost hollow centre of the kidney is where the urine collects. The cortex is the outermost tissue of kidney, it lies on top of the medulla.

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