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Part Three

- Physiological anatomy of the urinary system


Components of the urinary system:-

·  The kidneys are the excretory organs

·  The ureters are the ducts that carry secretions from the kidneys to the bladder

·  The bladder is the place where urine is collected

·  The urethra is the place through which urine exits the body

Urinary system function:-

Formation and secretion of urine and removal of waste and water in excess of the body’s need

Description of the parts of the urinary system:-

1- The kidneys:

·  There are two kidneys in the human body, each of which is 10-12 cm long, about 6 cm wide, and 2 cm thick. Each kidney weighs about 150 grams in men and 130 grams in women. They are located near the midline in the body, behind the peritoneal cavity of the posterior abdominal wall. The kidney The right kidney is lower than the left kidney by about 1.25 cm. In general shape, the kidney resembles a bean and is dark red in color. In the upper part of each kidney is the suprarenal gland. Each kidney consists of several units called nephrons, and each kidney contains from one million to 2 million nephrons, and it decreases. Their number depends on age or illness

College installation:-

The kidney is composed from the outside to the inside by:

1)    College portfolio

2)    The crust layer

3)    Medullary layer

·  Each kidney consists of a large number (one million - one and a half million) of tiny channels (nephrons or filters) connected by connective tissue. Each channel in the cortical layer begins with a crescent-shaped indentation called Bowman’s capsule, inside which there is a plexus of blood vessels starting from the incoming artery and ending with the outgoing artery. 

·   Bowman's capsule and the blood plexus are located inside tiny balls called Malpighian cells, and there are many thousands of these cells in the cortex.

·  From Bowman’s capsule emerges a tortuous canal called the tortuous duct. The first goes towards the medulla layer, forming the descending duct. Then it returns to the cortex again, forming the ascending duct. In the cortex, it winds upon itself to form the second tortuous duct. Finally, it returns to the medulla, where they gather to form urinary collecting ducts, each of which ends by opening. On the tops of the Pyramids of Malpighi in the Ureter Basin.

Kidney function in the body:

·  Normal kidneys perform four basic functions in the human body:-

-  Excretion of excess water from the human body

-  Ridding the body of toxins and secretions resulting from the food combustion process, such as:

·  Excretion of waste resulting from protein digestion in the body (such as urea and creatine)

·  Secretion of some ions and regulation of acid balance (PH) in the blood, such as (sodium - potassium - calcium - phosphorus - chloride - phosphate - and hydrogen)

·   Excretion of medications, toxins and chemicals that may harm the body

Hormonal function:-

The kidneys secrete three hormones:

·  Hormone (renin), which helps conserve the amount of fluids and sodium by regulating the hormone

·  Aldosterone is from the suprarenal gland, so the secretion of renin increases in the event of a lack of sodium in the blood or in a state of dehydration, so renin works to raise blood pressure, and thus the kidneys regulate the blood pressure of the human body.

·  The hormone erythropoietin stimulates the bone marrow to secrete red blood cells.

·  Activating vitamin D, which is necessary for the health of the mouth, teeth and bones.

·  A regulatory function to regulate the amount of fluids in the body.

·   Concentration of salts such as sodium and potassium, which regulate blood yellowness.

2- The Ureter

·   It is a muscular canal that delivers urine from the kidney to the bladder. It is 25 cm long and performs regular contractions from top to bottom to push urine into the bladder.

3- The Urinary Bladder:-

.    It is a muscular sac whose primary function is to store urine until it is time to expel it from the body through the urethra

4- The urethra:-

·    It is the canal that carries urine from the bladder to the outside of the body. It is different in men than in women, as it is 20 cm in men and only 4 cm in women.

Urine formation in the kidneys:

Urine is formed through three stages:

·   Filtration:- where water, salts and some other substances are filtered from the blood

·   Absorption: - Some of the water and salts that the body needs are reabsorbed into the blood

So that the blood components are not affected by losing all the water and salts dissolved in them

·   Excretion: It is carried out by the cells of the kidney tubules, which have the ability to test substances that exceed their quantity

The normal limit allowed in the body or when it is not needed and it is disposed of

Formation of urine. This occurs in healthy, unaffected kidneys

Characteristics of urine:-

Color          : yellow

Specific density: from (1005) to (1025)

Concentration: Acid about (PH = 6)

Smell: (Aromatic)

Content: Water + urea + creatine + ureate (protein product) and ions

ammonium

Inorganic substances: sodium - potassium - calcium - chloride - phosphate - sulfate

Exalates + about 100 gm protein (albumin) / 24 hours

The amount of urine in twenty-four hours (from half a liter to one and a half liters). This depends on the fluids entering and leaving the human body during the day, as well as the weather condition, the general health condition of the individual, and the condition of the kidneys in particular.