Urinary / Excretory System

Group 1

II- Aristotle

INTRODUCTION

As it functions, the body produces wastes,

which must be disposed of. One type of waste

is nitrogen-containing waste (such as urea and

uric acid), which results from the breakdown

of proteins and nucleic acids by the body cells.

Most people know that each person has two kidneys, their general location, and that they are essential to the maintenance of life, but fewer people are aware of the many functions he kidneys perform. Most people has a much better understanding of the function of the urinary bladder and the great appreciation for the attention that is required when it is filled with the urine produced by the kidneys.

Functions of the Urinary System 1. Excretion – the kidneys are the major

excretory organs of the body. They remove waste products, many are which of toxic, from the blood.

2. Regulation of blood volume and pressure – the kidneys play a major role in controlling the extracellular fluid volume on the body by producing either a large volume of dilute urine of small volume of concentrated urine.

3. Regulation of the concentration of solute in the blood – the kidneys help regulate the concentration of the major molecules and ions such as glucose.

4. Regulation of extracellular fluid pH- the kidneys secrete variable amounts of H+ to help regulate extracellular fluid pH.

5. Regulation of red blood cell synthesis – the kidneys secrete a hormone , erythropoietin, which regulate the synthesis of red blood cells in bone marrow.

6. Vitamin D synthesis – the kidneys play an important role in controlling blood levels Ca2+ by regulating the synthesis of Vitamin D.

Parts of the Urinary System

Parts of the urinary system

Major parts

Kidney – these are two bean shaped organs , each about the size of a clenched fist. They lie on posterior abdominal wall, behind the peritoneum , with one kidney on either side of the vertebral column.

Ureters- exist the kidney and connects to the urinary bladder. Urine passes from the tips of the renal pyramids into the calyces. From the calyces, the urine collects in the renal pelvis and exits the kidney through the ureter.

Urinary bladder- is a hollow muscular container that lies in the pelvic cavity just posterior to the pubic symphysis. It functions to store urine, and its size depends on the quantity of urine present.

Urethra - is a thin-walled tube that carries urine by peristalsis from the bladder to the outside of the body. At the bladder-urethra junction, a thickening of the smooth muscle forms the internal urethral sphincter. The length and relative function of the urethra differ in two sexes. In females, it’s about 3 to 4 cm. While in males , the urethra is approximately 20 cm.

1. Human urinary system:

2. Kidney, 3. Renal pelvis, 4. Ureter, 5. Urinary bladder, 6. Urethra. 7. Adrenal gland

Vessels: 8. Renal artery and

vein, 9. Inferior vena cava,

10. Abdominal aorta, 11. Common iliac artery and veinWith transparency: 12. Liver, 13. Large intestine, 14. Pelvis

Cross- Section of Kidney When the kidney is cut lengthwise, three

distinct regions become apparent. The RENAL CORTEX, is the outer region which

is light in color. RENAL MEDULLA, it is deep in the cortex

which is darker reddish-brown area. RENAL COLUMNS, cortex like tissue that

separates the medullary pyramids.

CALYCES, are extensions of the pelvis from cup-shaped areas that enclose the tips of the pyramids. It collects urine.

RENAL ARTERY, it is the arterial supply of each kidney.

INTERLOBAR ARTERY, it travels through the renal columns to reach the cortex.

ARCUATE ARTERIES, curve over the medullary arteries.

INTERLOBULAR ARTERIES, it branch of the arcuate arteries and run outward to supply the cortex tissue.

NEPHRONS

Each kidney contains over a million tiny structures called nephrons.

Nephrons are the structuraland functional units of the kidneys.

They are responsible for forming the urine product.

Each nephron consists of two main structures: a glomerulus, which is a knot of capillaries and a renal tubule. The closed and of the renal tubule is enlarged and cup-shaped and completely surrounds the glomerulus.

This portion of the renal tubule is called the glomerular (glom = little ball), or Bowman’s capsule.

The inner layer of the capsule is made up of highly modified octupuslike cells called podocytes. Podocytes have long branching processes that intertwine with another and cling to the glomerulus. Since openings or slits, exist between their extensions, the podocytes form a porous or holey membrane around the glomerulus.

Urine Formation

Urine formation is the result of three processes : filtration, reabsorption and secretion

Urine Formation

1. FILTRATION Is a non-selective, passive process The filtrate that is formed is essentially blood

plasma without blood proteins Both proteins and blood cells are normally too

large to pass through the filtration membrane and when either of these appear in the urine , it is pretty fair bet that there is some problem with the glomerular filters

Urine Formation

If arterial blood pressure drops too low , the glomerular pressure becomes inadequate to force substances out of the blood into the tubules , and filtrate formation stops.

Urine Formation

2. REABSORPTION It begins as soon as the filtrate enters the

proximal convoluted tubule. Water, glucose, amino acids and needed ions

are transported out of the filtrate into the tubule cells and then enter the capillary beds.

Urine Formation

3. SECRETION It is essentially reabsorption in reverse. Some substances such ashydrogen and

potassium ions and creatinine , move from the blood of the peritubular cappilaries throgh the tubule cells or from the tubule cells themselves into the filtrate to be eliminated in urine.

Urine Formation

This process seems to be important for getting rid of substances not already in the filtrate, such as certain drugs , or as an additional means for controlling blood pH.

CHARACTERISTICS OF URINE Fleshly voided urine is generally clear and pale

to deep yellow. The normal yellow color is due to urochrome ,

apigment that results from the body’s destructionof hemoglobin

The more solutes are there in urine, the deeper yellow its color, on the other hand, the dilute urine is a pale yellow, straw color.

CHARACTERISTICS OF URINE At times, urine may havean abnormal color. This

might be a result of eating certain foods (beets, for example) or the presence of bile or blood in the urine.

When formed, urine is sterile and its odor is slightly aromatic.

If it is allowed to stand, it takes on an ammonia odor caused by the action of bacteria in the urine solutes.

CHARACTERISTICS OF URINE Some drugs, vegetables (such as asparagus) ,

and various diseases (such as diabetes mellitus) alter the usual odor of urine

Urine pH is usually slightly acid (around 6) ,but changes in body metabolism and certain foods may cause it to be much more acidic or basic.

CHARACTERISTICS OF URINE For example, a diet that contains large

amounts of protein like eggs and cheese and whole wheat products causes urine to be quite acid ; thus such foods are called acid-ash foods. Conversely, a vegetarian diet is called an alkaline-ash diet because it makes urine quite alkaline as the kidneys excrete the excess bases.

CHARACTERISTICS OF URINE Bacterial infection of the urinary tract may also

cause the urine to be alkaline. Urine is more dense than distilled water. The term used to compare how much heavier

urine is than distilled water is specific gravity. Whereas the specific gravity of pure water is 1.0,

the specific gravity of urine ranges from 1.001 to 1.035

CHARACTERISTICS OF URINE Solutes normally found in urine include

sodium and potassium ions, urea, uric acid creatinine, ammonia, bicarbonate ions, and various ions depending on blood composition.

Solutes not normally found in urine are as follow:

Abnormal Urinary ConstituentsSUBSTANCES NAME OF CONDITION POSSIBLE CAUSES

GLUCOSE Glycosuria Nonpathologic:excessive intake of sugary foodsPathologic: diabetes mellitus

PROTEINS Proteinuria (also called albuminuria)

Nonpathologic : physical exertion, pregnancy, Pathologic: glumerulonephritis, hypertension

PUS (WBC’s and bacteria)

Pyuria Urinary Tract Infection (UTI)

RBCs Hematuria Bleeding in the urinary tract due to trauma, kidney stones and infection

HEMOGLOBIN Hemoglobinuria Various : transfusion reaction , hemolytic anemia

BILE PIGMENT Bilirubinuria Liver disease or hepatitis