Urinary system

 

Urinary system:- Urinary system is a set of biological organ that mainly act in production of urine, storage of urine and elimination of urine. It consists by the a pair of kidney, a pair of urater, a bladder and a urethra. 

The function of urinary system 

• Remove waste products and medicines from the body

• Balance the body's fluids 

• Balance a variety of electrolytes

• Release hormones to control blood pressure

• Release a hormone to control red blood cell production

• Help with bone health by controlling calcium and phosphorus

Kidneys:- This pair of reddish brown in colour and organs is located below the ribs toward the middle of the back.

The kidneys remove urea from the blood through tiny filtering units called nephrons. Each nephron consists of a ball formed of small blood capillaries (glomerulus) and a small tube called a renal tubule. Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney.

Ureters:- These narrow tubes carry urine from the kidneys to the bladder. Muscles in the ureter walls keep tightening and relaxing. This forces urine downward, away from the kidneys. If urine backs up, or is allowed to stand still, a kidney infection can develop. About every 10 to 15 seconds, small amounts of urine are emptied into the bladder from the ureters.

Bladder:- This triangle-shaped, hollow organ is located in the lower belly. It is held in place by ligaments that are attached to other organs and the pelvic bones. The bladder's walls relax and expand to store urine. They contract and flatten to empty urine through the urethra. The typical healthy adult bladder can store up to 2 cups of urine for 2 to 5 hours.

Sphincter muscles:- These circular muscles help keep urine from leaking by closing tightly like a rubber band around the opening of the bladder.

Nerves in the bladder:- The nerves alert a person when it is time to urinate, or empty the bladder.

Urethra:-  This tube allows urine to pass outside the body. The brain signals the bladder muscles to tighten. This squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra. When all the signals happen in the correct order, normal urination happens.

Urine and it's function 

Urine:- Urine is a clear fluid amber colour due to urobiling pigment. It composed by water 💦, amonia  and other ions.

Gravity of urine:- 1020 - 1030

pH of urine:- 4.5 to 8

Per day urine production :- 1000 ml to 1300 ml

Composition of urine:- Water 96%, uria 2% and other ions 2% ( sodium, phosphate, urine acid etc )

Function of urinary system

° It maintain the water and electrolyte.

° It regulate acid, bace balance

° Production and secration of erithroprotein. 

° Production and secration of renin

Kidney

Kidney:- Kidney is also known as renal. it is a bean shaped small organ. It has pair in human body. It is a principal organ of urinary system. It is reddish brown in colour.

Length:- 11 cm

Width:- 6cm

Thickness 3 cm

Location of the kidney :- Kidney located in posterior abdominal wall, each side of the vertebral column (T4-L3)    

° Right kidney :- Posterior of the liver   

° Left kidney :- Posterior of the spleen

Structure of the kidney

 Or 

Gross structure of kidney 

Or 

Microscopic structure of kidney

CORTEX:- A reddish brown layer of tissue, immediately below the capsule and outside the renal pyramids

MEDULLA:-The innermost layer, consisting of pale conical shaped striations, the renal pyramids

HILUM :- Is  the concave medial border of the kidney where the renal blood and lymph vessels, the ureter and nerves enter

• Urine formed within the kidney passes through a renal papilla at the apex of a pyramid into a major calyx

Several minor calyx merge into a major calyx and two or three major calyces combine forming the renal pelvis, a funnel shaped structure that narrows when it leaves the kidney as the ureter

The walls of the calyces and renal pelvis are lined with transitional epithelium and contain smooth muscle

Peristalsis, intrinsic contractions of smooth muscle, propels the urine through the calyces, renal pelvis and ureters to the bladder

MICROSCOPIC STRUCTURE

• The kidney contains about 1-2 million functional units, the NEPHRONS and smaller number of collecting ducts

• The collecting ducts transport urine the pyramids into the calyces, giving the pyramid their striped appearance

• The collecting ducts are supported by connective tissue, blood vessels, nerves and lymph vessels

Urine Transport 

Nephron

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Minor colyx

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 Masor colyx 

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Rinel

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 Hillum

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Urethra 

Blood supply to kidney 

Aorta

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Left and right branch of renal artery 

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Segmental artery

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Intra lobar artery ( cortex or pyramid )

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Inner lobular artery 

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 Efferent artery

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 Glomerular filtration 

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Afferent artery

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Inner lobular vein

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 Intra lobar vein

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Segmental vein

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Renal vein

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Vena cava

Function of Kidney

1. Production of urine

2. Balanced water and electrolyte

3. Production and secration of erithroprotein

4. To maintain body temperature

Longitudinal section of kidney

1. Outer fibrous capsule

2. Renal cortex

3. Inner medulla

Outer fibrous capsule:- Outer fibrous capsule capsule: is the deeper layer and it's smooth, transparent, fibrous membrane that is continuous with the coat of the ureter. It serves as a barrier against trauma and helps to maintain the shape of the kidney.

The renal cortex: is part of the kidneys it's reddish area containing mostly nephrons and blood vessels. Its function is to filter the blood and remove waste products inside the body.And a deep reddish- brown region called Renal medulla within the medulla 8-18 cone-shaped structures termed renal pyramids. The base of each pyramid faces the renal cortex and it's apex called renal papilla (points toward the center of the kidney.

Renal Pelvis:- Area through which artery, veins and nerves enter and leave kidney.