BIOL 4003 Urinary System

- Modified smooth muscle cells of afferent arteriole - Located near entrance to renal corpuscle at vascular pole - Contract when stimulated by stretch or sympathetic stimulation - Synthesize, store, and release renin

Granular Cells of the Juxtaglomerular 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

Macula Densa of the Juxtaglomerular Apparatus

They support the capillaries of the glomerulus, have contractile properties that allow them to help regulate capillary diameter and filtration rate, and have regulatory functions including protection/phagocytosis and secrete cytokines and other cell-communication chemicals.

Mesangial cells are found in the _______________ corpuscle.

U: mucosa with the urothelium LP: lamina propia S: submucosa IL: inner smooth muscle layer ML: middle smooth muscle layer OL: outer smooth muscle layer

Micrograph of Bladder Wall and Urothelium:

able to see the pale staining columnar principal cells

Micrograph of Collecting Ducts:

Image A

Micrograph of Renal Corpuscle:

CD: collecting ducts Notice the tall cuboidal/low columnar epithelium and the very prominent and visible lines separating cells at their lateral borders. Also note that the cells can appear to "bulge" into the lumen.

Micrograph of Renal Medulla:

Thin: - Thin Limb of Loop of Henle: ascending and descending portion are histologically identical and cannot be differentiated. Simple squamous lining similar to capillaries. Thin limb will be larger than a capillary and will not have rbcs. Compare to lining of vasa recta in micrograph Ascending: Thick Limb of the Loop of Henle: simple cuboidal lining Collecting: Collecting duct: lined with pale staining taller cuboidal to low columnar epithelial cells, with very visible lateral cell borders (lines between cells). Cells (principal cells) may be slightly bubble shaped and bulge into the lumen.

Micrograph of Renal Medulla:

- Renal papilla shown within bracket. - Collecting ducts fuse into papillary ducts that dump urine out the renal papilla into a minor calyx. - Minor calyx labeled with stars. As the collecting ducts coalesce into papillary ducts, the epithelial lining may become stratified. This will be seen closer to the renal papillae.

Micrograph of Renal Papilla:

pg. 408

Micrograph of Renal Papilla:

Mu: muscularis M: mucosa A: adventitia

Micrograph of Ureter Cross Section:

pg. 406

Micrograph of the Juxtaglomerular Apparatus:

In the cortex, peritubular capillaries branch off of the efferent arterioles supplying the tissue near the glomerulus, the proximal and distal convoluted tubules In the medulla, the efferent arterioles give rise to the vasa recta, supplying the nephron loop portion of the nephron

Renal Circulation Diagram:

made of cone shaped masses of tissue that look like petals in a cross section view

Renal Medulla...

tuft of glomerular capillaries, surrounded by a double-walled epithelial capsule called the glomerular (Bowman) capsule

The renal corpuscle consists of the

capillary network that is the site of blood filtration with an enclosing capsule; also called the malpighian body; blood filtering component of the nephron of the kidney

The renal corpuscle is a

metabolic

We will focus on the kidney, as it is the major _____________________ organ of the urinary system that performs urinary functions.

At

Afferent is going

Exiting

Efferent is

1. Outer Cortex 2. Inner Medulla

What are the two layers of the kidneys?

the central space or cavity where urine is collected

Renal Pelvis...

nephron (it is microscopic)

What is the functional filtration unit of the kidney?

cortex

All of the corpuscle and most of the tubules reside in the ________________.

homeostasis

Basically, the urinary system's main purpose is to maintain the body's ________________________. In other words, the urinary system's main function is to maintain the body's acid-base balance.

U: urothelium LP: lamina propria S: submucosaI L: inner longitudinal muscle ML: middle circular muscle OL: outer longitudinal muscle A: adventitia

Bladder Micrograph:

Baroreceptors of afferent arteriole sense decreased pressure and stimulate sympathetic stimulation and stimulate JG cells to release Renin Renin released into the blood will cleave the plasma protein, angiotensinogen, into angiotensin I Angiotensin I is converted into active angiotensin II by Angiotensin Converting Enzyme (ACE) within the epithelium of the lung Angiotensin II causes systemic blood pressure to go up by - Stimulating vasoconstriction of vessels - Stimulating aldosterone release from adrenal (aldosterone promotes sodium and water reabsorption from DCT and CD) - Stimulates thirst centers to increase drinking

Blood Pressure

renal corpuscle

Blood is filtered within the __________ _____________________________ across the glomerular capillary bed.

Yes

Can collecting tubules and ducts be found in the renal medulla and the renal cortex?

Numerous collecting ducts converge toward the tip of the medullary pyramid - Papillary ducts formed by merger of several collecting ducts - 30 or so papillary ducts end in the tip of each papilla - Collecting and papillary ducts lined with simple cuboidal epithelium composed primarily of principal cells. Principal cells lightly staining are specialized for water reabsorption and contain lots of aquaporins. Intercalated cells are rare but stain more darkly.

Collecting System

The wide base of each renal pyramid sits next to the cortex and the border between the two is described as the corticomedullary junction. Each renal pyramid comes to a point called the renal papilla. The renal papilla serves as the location where urine is emptied into a series of tubular transporting structures starting with the minor calyces. There is one minor calyx surrounding and collecting urine from each renal papilla. Minor calyces fuse with major calyces which eventually dump urine into a dilated space called the renal pelvis. The renal pelvis is drained by a ureter. The region where the ureter leaves the kidney and the vessels enter and leave is called the renal hilus (or hilum).

Detailed description of the kidney:

from the module

Detailed diagram of the Renal Cortex:

Cuboidal epithelium without microvilli Functions in reabsorption of salts/electrolytes and some secretion

Distal Convoluted Tubule (DCT)

filtration

Example of substances filtered by ___________________ membrane:

pg. 398

Figure 19.5 Renal Corpuscles:

Filtration occurs across the glomerular filtration membrane. This is composed of the endothelium of the glomerular capillaries, the fused basement membrane of the endothelium/podocytes (glomerular basement membrane, GBM), and the filtration slits created by the podocytes. The glomerular capillaries are fenestrated capillaries (remember fenestrated capillaries? They have transcellular pores/fenestrations that increase exchange).

Filtration Membrane:

Figure 19.19 pg. 407

Fluid Transport in the Urinary System:

includes darker renal pyramids and interposed renal columns of supporting cortical tissue that extends into the medulla.

Inner Medulla of the kidney:

Renal Cortex

Label the PCT and the DCT of the....

P: Proximal convoluted tubule, simple cuboidal epithelium with abundant cytoplasm, stains very pink with H&E, abundant microvilli of the brush border may appear as pink debris within the tubule lumen D: Distal convoluted tubule, simple cuboidal epithelium with less cytoplasm, appears as slightly shorter cuboidal epithelium with abundant nuclei, no microvilli debris within lumen G: glomerulus U: urinary space (capsular space) TP: tubular pole, where the proximal convoluted tubule drains the glomerulus

Label the micrograph of the Renal Cortex: G: U: TP: D: P:

P: Proximal convoluted tubule, simple cuboidal epithelium with abundant cytoplasm, stains very pink with H&E, abundant microvilli of the brush border may appear as pink debris within the tubule lumen D: Distal convoluted tubule, simple cuboidal epithelium with less cytoplasm, appears as slightly shorter cuboidal epithelium with abundant nuclei, no microvilli debris within lumen

Label the micrograph of the Renal Cortex: P: D:

Descending limb and ascending limb - Thick segments: simple cuboidal epithelium Initial part of descending limb and part or all of ascending limb Active transport of salts/electrolytes out of tubule - Thin segment: simple squamous epithelium Lower part of descending limb Cells very permeable to water, passive reabsorption of sodium and chloride

Loop of Henle (Nephron Loop)

Image B

Micrograph of Renal Corpuscle:

L: lumen E: urethral epithelial (stratified columnar in some areas and pseudostratified columnar elsewhere, becomes stratified squamous at the distal end.)

Micrograph of Urethra:

A cross section through a medullary renal pyramid shows the simple squamous epithelium of the thin descending and ascending limbs of loops of Henle (T) and its thick ascending limbs (A), as well as the pale columnar cells of collecting ducts (CD). Note also the homogeneous interstitium with capillaries smaller than the thin limbs.

Micrograph of a cross section of the renal medulla:

you will see that it consists almost entirely of a ball of capillaries (glomerulus, G) surrounded by two layers of capsule, both visceral and parietal(PL) The space between the layers is the capsular space (CS) and is the location where the fluid filtered out of the capillaries is first captured and contained. The capsular space is often called Bowman's capsule. On the left-hand side of image (a), you will see a tubule connecting to the capsular space. This is the beginning of the tubular system of the kidney and is called the proximal (meaning close to the origin) convoluted (meaning twisty) tubule. The region where the proximal convoluted tubule attaches to the corpuscle is called the tubular pole. The arterioles entering and leaving the corpuscle may be seen on the opposite side. This is called the vascular pole. A region of the distal convoluted tubule is shown between the afferent and efferent arterioles and contains a region of closely packed elongated cells called the macula densa. The macula densa is shown in the light micrograph at (MD). Finding these tightly packed cells is sometimes the easiest way to locate the vascular pole of the renal corpuscle as the arterioles might be obliqued and difficult to locate.

Micrograph of the Renal Corpuscle:

a) Medullary renal pyramid cut transversely shows closed packed cross section of the many nephron loops thin descending and ascending limbs (T) and thick ascending and descending limbs (A), intermingled with parallel vasa recta capillaries containing blood (C) and collecting ducts (CD). All these structures are embedded in the interstitium (I), which contains sparse myofi-broblast-like cells in a matrix very rich in hydrophilic hyaluronate. The specialized nature of the interstitial tissue helps maintain the osmolarity gradient established by differential salt and water transport across the wall of the nephron loop, which is required to concentrate urine and conserve body water.

Micrograph of the Renal Medulla and Collecting Ducts:

b) The TEM reveals the slightly fibrous nature of the interstitium (I) and shows that the simple squamous epithelium of the thin limbs (T) is slightly thicker than that of the nearby vasa recta capil-laries (C).

Micrograph of the Renal Medulla and Collecting Ducts:

b) Empty - Mucosa highly folded and urothelium has mulbous umbrella cells c) Full - the mucosa is pulled smooth and the U is thinner

Micrograph when bladder is empty v. full:

as shown on pg. 397 of the book

Microvasculature of the Renal Cortex

- Stratified lining of large papillary duct shown at arrow. - Simple columnar lining of the renal papilla. - Urothelium shown at arrows - lines minor calyx and the rest of the transporting structures between the renal papilla and the bladder.

Minor Calyx Micrograph:

cortical nephrons

Most nephrons are contained within the cortex and are called...

Diagram of a nephron shows levels of the sections in the photos.

Nephron Components:

The podocytes form the visceral layer of the glomerular capsule. Podo-cyte literally means foot-cell. Podocytes have hundreds of foot-like processes called pedicels that interdigitate with adjacent pedicels and form filtration slits between them. Most large substances are held back and not filtered out of the blood but small substances are freely filtered out. Typically, protein is unable to cross the filtration membrane and therefore does not appear in normal/healthy urine.

Podocytes create the filtration slits within the filtration membrane:

the outer layer material of the kidney and is found in between each section known as the renal medulla

Renal Cortex...

pg. 399

Substances filtered by filtration membrane in the glomerular filtration barrier:

The glomerular filtration barrier consists of three layered components: the fenestrated capillary endo-thelium, the GBM, and filtration slit diaphragms between pedicels. The major component of the filter is formed by fusion of the basal laminae of a podocyte and a capillary endothelial cell.(a) TEM shows cell bodies of two podocytes (PC) and the series of pedicels on the capillary (C) basement membrane separated by the filtration slit diaphragms. Around the capillaries and podocytes is the capsular space (CS) into which the filtrate enters. The enclosed area is shown in part (b). (X10,000)(b) At higher magnification, both the fenestrations (F) in the endothelium (E) of the capillary

The Glomerular Filtration Barrier:

Simple cuboidal epithelium with prominent microvilli to facilitate resorption About 65% of all water and electrolytes in the filtrate and all of the organic nutrients in the filtrate are reabsorbed here. Some secretion occurs (H+, NH4+, and other ions).

The Proximal Convoluted Tubule (PCT)

toxins

The Urinary, or Excretory System is another system by which the body rids itself of unwanted ___________ or (waste).

medulla; cortex

The _____________ is seen at the top of the field of view. The _______________ is seen at the bottom of the field of view.

renal

The ______________ tubules are a set of tubules that transport filtered fluid and modify it to produce urine.

Soft paired retroperitoneal organs found on the right and left of the abdominal aorta near the inferior border of the liver. Consists of an outer fibrous capsule and a parenchyma composed of two regions/layers.

The kidneys are

three

The male urethra has ______________ regions, the prostatic urethra that begins at the bladder and travels through the prostate, the membranous urethra, a short region in between the prostate and the penis, and the penile or spongy urethra that travels through the penis.

longer

The male urethra transports both urine and ejaculate and is ____________ that the female urethra. This likely contributes to the reasons why urinary tract infections are less frequent in the male, bacteria have a longer way to travel from the outside environment into the bladder.

c) Diagram shows the major structural differences between the cuboidal cells of proximal and distal tubules. Cells of both tubules have basal membrane invaginations associated with mitochondria.

The micrograph comparing convoluted tubule epithelia:

(b) A section of cortical tissue shows one renal corpuscle (RC), the wide, eosinophilic proximal convoluted tubules (PCT) with the smaller, less well-stained distal convoluted tubules (DCT).

The micrograph of the renal cortex shows:

renal corpuscle and the renal tubule

The nephron consists of the

excretion - separation of wastes from the body fluids and the elimination of them; mostly metabolic nitrogenous wastes and excess water

What is the main function of the urinary system?

medullary

The renal tubules start at the ___________ Capsule and ends at the tip of the medullary pyramid.

deep

The wall of the minor calyx contains dense connective tissue and adipose __________ to the urothelium.

PCT and DCT (pg. 402)

This micrograph shows the...

the PCT has microvilli while the DCT does not

What is the major difference between the PCT and the DCT?

the kidney

What is the major metabolic organ of the urinary system?

transitional

Urothelium is ______________________ epithelium that can resemble stratified squamous epithelium when stretched but has rounded surface cells (umbrella cells) when not stretched.

1. Elimination of biologically active molecules: hormones, drugs 2. Regulation of water balance 3. Regulation of ion levels: Na+, K+, Ca2+ 4. Regulation of acid - base balance: alters levels of H+ and HCO3- 5. Regulation of blood pressure: produces Renin which stimulates the production of Angiotensin II 6. Formation of calcitriol (active vitamin D, 1,25 dihydroxy vitamin D3): regulates blood calcium levels 7. Production and release of erythropoietin: Secretes erythropoietin (EPO) in response to low blood oxygen; stimulates red bone marrow to increase erythrocyte production] 8. Potential to engage in gluconeogenesis: During prolonged fasting or starvation; produces glucose from noncarbohydrate sources; maintain glucose levels

What are other functions of the urinary system?

1. Granular cells 2. Macula densa

What are the components of the juxtaglomerular apparatus?

1. Parietal (outer) layer 2. Visceral (inner) layer - composed of podocytes 3. Capsulate space - contains filtrate

What are the layers of the Bowman's Capsule?

2 kidneys, 2 ureters, 1 bladder, 1 urethra

What are the six organs of the urinary system?

Just outside glomerulus In gap between afferent arteriole and efferent arteriole Communicate with other cells of JG apparatus and provide support Function incompletely understood

What do extraglomerular mesangial cells do?

filter blood, remove waste products and convert filtrate into urine

What do the kidneys do?

transport urine from kidneys to urinary bladder

What do the ureters do?

Helps regulate blood filtrate formation & systemic blood pressure

What does the juxtaglomerular apparatus do?

artery --> capillary (glomerulus) --> artery --> capillary --> vein

What is the arrangement of circulation that is special in the kidneys?

- They have longitudinally folded mucosa (M) that is surrounded by a thick muscularis (Mu) layer that contracts in a wave link fashion called peristalsis. - The outer layer is the adventitia (A). - The mucosa of the ureter consists of a urothelium (transitional epithelium) and lamina propria.

What is the characteristic pattern of the ureter?

an expandable muscular sac, stores as much as 1 L urine

What is the function of the bladder?

eliminates urine from body

What is the function of the urethra?

Urine = filtration - reabsorption + secretion

What is the urine formula?

Minor calyces

_________ _______________________ collect urine from renal papillae and run together into major calyces which all dump their fluid into the renal pelvis. From the renal pelvis, urine is drained out of the bladder by a ureter and transported to the bladder for storage until micturition (urination).

Juxtamedullary

______________ nephrons have their renal corpuscle located in the cortex at the corticomedullary junction and have long renal tubules that extend into the medulla

Peristaltic

________________________ waves of muscle contraction move urine from the kidney to the bladder.