Labeling exercise micturition reflex

• http://highered.mheducation.com/sites/0072507470/student_view0/chapter26/labeling_exercises.html#

• http://highered.mheducation.com/sites/0072507470/student_view0/chapter26/labeling_exercises.html#

http://highered.mheducation.com/sites/0072507470/student_view0/chapter26/animation__micturition_reflex.html

S Naghma Rizvi

June, 2015

Acknowledgement Muhammad Nisar

*Urinary System

Objectives

At the end of this session students will be able to: Define the Urinary System. List the organs of Urinary system Understand the functions of the urinary system Explain how kidney contributes to homeostasis Describe the location of the kidney. Describe the :

gross structure of kidney microscopic structure of kidney.

Objectives Discuss the role of each component of nephron in

terms of : Filtration selective reabsorption & secretion involved in the formation of urine.

Briefly discuss the role of kidney in maintaining water and electrolyte balance.

Discuss the structure and functions of Ureters Urinary bladder Urthera Briefly the process of micturition

Urinary System

The urinary system plays a vital part in maintaining homeostasis of water and electrolyte concentrations within the body. The kidneys produce urine that contains metabolic waste products, including the nitrogenous compounds urea and uric acid, excess ions and some drugs.

Urinary system VDO

Organs of Urinary SystemThe urinary system is the main excretory system and consists of the following structures: 2 kidneys, which secrete urine

2 ureters, which convey the urine from the kidneys to the urinary bladder

The urinary bladder where urine collects and is temporarily stored

The urethra through which the urine passes from the urinary bladder to the exterior.

Functions of Urinary System (FRS)

1. Filtration of the blood by removing toxins or waste.

2. Reabsorption of vital nutrients, ions and water by conserving important materials

3. Secretion of excess materials by preventing a build-up of certain materials in the body such as drugs, waste, etc.

Functions…

Activation of Vitamin D

Active Vitamin D (D3) assists homeostasis by increasing calcium absorption from the digestive tract

Release of Erythropoietin by the kidney

New RBCs assist homeostasis by ensuring adequate Oxygen and Carbon Dioxide transport

Release of Renin by the kidney

• Renin stimulates the formation of a powerful vasoconstrictor called Angiotensin II

• Angiotensin II assists homeostasis by causing vasoconstriction which increases blood pressure

Secretion of H (+1) and reabsorption of HCO3 (-1)

Eliminates excess hydrogen ions and conserves buffer material such as bicarbonate hence controlling acid/base conditions in body fluids

Location of kidney

Location of Kidney• Kidney lie on the posterior abdominal wall one on each

side of the vertebral column behind the peritoneum and

below the diaphragm.

• They extend from the level of 12th thoracic vertebrae

to the third lumber vertebrae receiving some protection

from lower rib cage

• Right kidney is slightly lower then the left because of

considerable space occupied by the liver.

Structure of Kidney Bean shaped organ, weighs 150g

Length 11cm Width 6cm Thickness 3cm

Three layers of tissue surrounds each kidney Renal capsule (innermost)

Adipose capsule

Renal Fascia (outermost)

These layers protect, maintains shape, and anchors kidney with the posterior abdominal wall

Gross Structure of Kidney

Gross Structure of KidneyFibrous capsule: Surrounds the kidney

Cortex: Reddish brown layer of tissue immediately below the capsule. Portion of cortex b/w pyramids called renal column.

Medulla: They are 8-18 in number . It forms the inner most layer consisting of pale conical shape structure called renal pyramids have an apex & base.

Renal papilla: It is the apex of pyramids

Renal lobe: Consists of renal pyramid, its overlaying area of renal cortex and one half of each adjacent renal column.

Hilum: The concave medial border of the kidney where the renal blood and lymph vessels, the ureter and nerve enter. The hilum expand into a cavity called renal sinus

Renal pelvis: Funnel shaped structure which receive urine formed by the kidney is called pelvis. It has a number of distal branches called calyces.

Minor calyx: It is the region after the papilla.

Major Calyx: Minor calyx joins to form major calyx

Each kidney has 8-18 minor calyces and 2-3 major calyces.

Blood supply to the kidney

• https://www.wisc-online.com/learn/natural-science/life-science/ap2504/the-vascular-system-of-the-kidneys

Microscopic structure of kidney

Each kidney is composed of about 1–2 million functional units, the nephrons, and a smaller number of collecting ducts.

Each nephron consists of:

1. Renal corpuscles (close end)

2. Renal tubules (open end)

Renal Corpuscles• The two components of renal corpuscles are:

glomerulus (capillary network) glomerular (Bowman) capsule.

Note the difference in the diameters of the afferent and the efferent arteriole

Renal TubulesRenal tubule consists of the three parts:

Proximal convoluted tubuleIt is attached to the glomerular capsule, it is tightly coiled rather then straight

Loop of HenleIt the proximal and distal convoluted tubule. Its first part called descending limb of LOH, dips into the renal medulla, it then make turn and return to renal cortex as a ascending limb of LOH

Distal convoluted tubuleThis part away from glomerular capsule

Cortical and Juxtamedullary NephronsCortical nephron

They are 80-85%. Their renal corpuscle lie in the cortex and they have short LOH that lie mainly in the cortex and penetrate only in the outer region of medulla

Juxtamedullary nephron:

They are 15-20%.The renal corpuscle of these nephron lie deep in the cortex near medulla and they have long LOH that extend into the deeper region of the medulla.

Histology of Nephron:Glomerular capsule consists of visceral and parietal layer.

Visceral layer consists of modified simple squamous epithelial cells called Podocytes. Many foot like projection of these cells (pedicels) wrap around the single layer of endothelium of the glomerular capillaries.

VISCERAL LAYER

PARIETAL LAYER

Parietal Layer

The parietal layer of glomerular capsule consists of simple squamous epithelium and form the outer wall of the capsule.

Fluid filter in the glomerular capillaries enter into the capsular space and then to the renal tubules.

Juxtaglomerular Apparatus

It consists of: • Specialized macula densa cells • Specialized granular juxtaglomerular (JG) cells

Macula Densa Cells:

The ascending limb of LOH make contact with afferent arteriole, here the columnar tubule cells become crowded which are known as macula densa.

Juxtaglomerular cells

Along side the macula densa the wall of afferent arteriole contains modified smooth muscle fibers called juxtaglomerular cells.

* The Juxtaglomerular Apparatus

Afferent Arteriole

Efferent Arteriole

Ascending limb of LOH

Macula Densa Cells

Granular Juxtaglomerular (JG) Cells

PCT

Bowman’s Capsule

Functions of Juxtaglomerular Apparatus

The JGA helps regulate blood pressure

https://www.wisc-online.com/learn/natural-science/life-science/ap2204/the-juxtaglomerular-apparatus

* The Juxtaglomerular Apparatus

Afferent Arteriole

Efferent Arteriole

Ascending limb of LOH

Macula Densa Cells

Granular Juxtaglomerular (JG) Cells

PCT

Bowman’s Capsule