Anatomy of a kidney Flashcards
What is the function of a nephron
take simple filtrate of the blood and modify it into urine
What are the three principle functions of nephrone
- Filtration
- Reabsorbtion
- Secretions
What are the secondary functions of nephrons
- Blood pressure * production of renin
- Red blood cell production
- Calcium absorption - converstion of calcidol into calcitiol- active form of vitamin D
What is the glomerulus
- tuft of capellaries surrounded by Bowmans capsule
* high pressure capillary bed between afferent and efferent arterioles
What type of cell tissue is the parietal layer of the Bowmans capsule
Simple Squamous Epithelium
What are the cells in the Bowmans capsule that wrap around the capillaries of the glomerulus
Podocytes - extensions are called pedicels
What do podocytes form on the glomerular capillaries
Filtration slits - small slits that plasma filters between to be captured by the Bowmans capsule and funneled to the PCT ( proximal convuluted tubule)
As blood passes through the glomerulus what percentage of plasma filters between the filtration slits/ sieves
10 - 20% captured by Bowmans capsule and funneled to Proximal convoluted Tubule
What three features comprise what is known as the filtration membrane?
- fenestrations and podocyte fenestra
- fused basement membrane
- filtration slits.
What size are the pores in the filtration membrane that permit rapid movement of filtrate from capillary to capsule?
70nm diameter
Fenestrations do what
- prevent filtration of blood cells or large proteins
- allow substances to diffuse from the blood based primarily on size
- less than 4nm - 8nm cross readily and freely
What type of charge to the protein associated with fenestrations have?
Negative charges - repel negatively charges substances, allow positively charged substances to pass easily
What does the basement membrane do?
Prevents filtration of medium to large proteins like globulins
Wht are Mesangial cells?
Cells in filtration membrane that contract to help regulate the filtration of the glomerulus
Filtration is regulated by what?
- Fenestrations in capillary endothelial cells
- Podocytes with filtration slits
- Membrane charge
- Basement membrane between capillary cells
What lies outside the Bowmans capsule and glomerulus?
The Juxtaglomerulus Apparatus JGA
What is the Macula Densa
- wall of distal convoluted tubule that makes up part of Juxtaglomerulus Apparatus
- Cuboidal epethelial cells
- monitors fluid composition of fluid flowing through DCT
- release paracrine signals (ATP & adenosine) in response to Na+ and rate of fluide
What do the Juxtaglomerulus cells do
- smooth muscle cell
- in afferent arteriole
- contracts or relaxes in response to ATP or adenosine released by Macula densa
- regulate blood flow to the glomerulus
If osmolarity of filtrate is hypersmotic (too hgiht) what happens?
Juxtaglomerular cells contract
decreases filtration rate so less plasma is filtered
less urine formation and greater retention of fluid
What happens when osmolarity goes down
- filtration and urine formation increase
* water lost by way of urine
What is a second function of macula densa cells
regulate renin release from juxtaglomerulus cells in afferenent arteriole
How many amino acids make up renin
304
What is renin
a enzyme that breaks down angiotensinogen to produce angiotensin 1
What are the steps of breaking down angiotensinogen
- Juxtaglomerular cells secrete renin
- Kidney releases renin into blood stream
- renin breaks down angiotensinogen into angiotensin 1
- ACE from pulmonary blood converst angiotensin 1 into angiotensin 2
- Angiotensin 2 helps regulate blood pressure by increasing it & stimulates the steroid hormone aldosterone from adrenal cortex
- Aldosterone stimulates sodium reabsorbtion by kidney which results in water retention and increased blood pressure
