Urinary system

The urinary system consists of:

• - Two kidneys: this organ extracts wastes from the blood, balance body fluids and form urine.

• - Two ureters: this tube conducts urine from the kidneys to the urinary bladder.

• - The urinary bladder: this reservoir receives and stores the urine brought to it by the two ureters.

• - The urethra: this tube conducts urine from the bladder to the out side of the body for elimination

Functions of the urinary system:

• 1. Excretion of wastes • 2. Hormonal production (rennin(肾素）-

angiotensin9血管紧缩素）and erythropoietin红细胞生成素)

• 3. Acid base balancing

Kidney

Ureter(20-30cm )

Bladder

Urethra( F 3-5cm M 16-22cm)

Cover

Renal capsule

Perirenal fat

renal fascia

Renal pelvis肾盂

Renal cortex

Renal medulla

Renal corpuscle肾小体

Renal tubules

Renal pyramid

Renal papillae 肾乳头

Kidney

Renal hilum 肾门 Renal Artery

Renal Vein

Calyces肾盏

Kidney

• A pair of reddish brown, bean shaped organ located in the posterior wall of the abdominal region, one in each side of the vertebral column.

• They usually span between T12 to L3. They are protected at least partially by the last pair of ribs and capped by the adrenal gland.

• The bean shape of the kidney is medially concave and laterally convex. On the medial concave border is the hilus where blood vessels, nerves & ureters enter and leave the kidney.

Internal Anatomy of the kidney • The renal pelvis is the large collecting space with in the kidney

formed from the expanded upper portion of the ureters. The pelvis branch to 2-3 major calyces and 8 to 18 minor calyces.

• The Renal medulla is the middle portion of the kidney. It consists of 8 to 18 renal pyramids, which are longitudinally striped, one cone shaped area. The base of each pyramid is adjacent to the outer cortex. The apex of each renal pyramid ends in papilla, which opens to a minor calyx. Pyramids contain tubules and collecting ducts of the nephron. Tubules involved in transportation and re-absorption of filtered materials.

• The renal cortex is the outermost portion of the kidney. It contains Renal tubules and Nephron (Renal corpuscle).

Nephron (Renal corpuscle)

• The basic functional unit of the kidney is the nephron（肾小球）.

• Each nephron is an independent urine-forming unit. Each kidney contains approximately one million nephrons.

Renal corpuscle

Functions of the kidneys

1. To the elimination of wastes 2. Regulation of total body water balance. 3. Control of the chemical composition of the

blood and other body fluid 4. Control of acid base balance

Urine formation

• The processes in urine formation are:

1. Blood filtration, every day the kidneys filter 1700 Liter of blood

2. Tubular re-absorption 3. Tubular secretion

Ureters

• Attached to each kidney is a tube called the ureters.

• Ureters transport urine from the renal pelvis to the urinary bladder.

• It is narrow at the kidney and widen near the bladder.

Urinary bladder

• Urinary bladder is a hollow, muscular organ that collects urine from the ureters and store until it is excreted.

• It usually accumulates 300 to 400 m.l. of urine but it can expand as much twice.

• It is located on the floor of the pelvic cavity. • In males it is anterior to the rectum and above

the prostate gland. • In females, it is located somewhat lower, anterior

to the uterus and upper vagina.

wall of urinary bladder

• The wall of urinary bladder is composed of three layers:

• 1) Mucosa, the innermost layer lined with transitional epithelium.

• 2) Muscularis, the middle layer, three layers of smooth muscle. This collectively called deterusor muscles逼尿肌.

• 3) Serosa (浆膜), the outer layer covers only the upper and lateral surfaces of the bladder.

Urethra • Urethra is a tube of smooth muscle lined with

mucosal layer. • It joins the bladder at its inferior surface and

transport urine out side the body during urination. • It is 3-5cm in female and 16-22 cm in length in male. • In females it opens between vagina and clitoris. In

male it pass through prostate, membranous portion (pelvic diaphragm muscle), spongy portion (that pass through corpus spongosus) and open at the tip of penis.

Urine & urination • Composition of urine varies depending on the

diet, exercise, water consumption and other factors. However, it is composed of mainly water, urea, chloride, potassium, sodium, phosphate and uric acid.

• Proteins, glucose, cells and calculi from minerals are abnormal if present in urine.

• The PH of urine is 5.0 to 8.0 (mostly acidic) and has translucent (clear, not cloudy) color.

Urine & urination • To maintain the proper osmotic concentration of

the extra cellular fluid to excrete wastes and to maintain proper kidney function the body must excrete at least 500ml of urine per day.

• A healthy person excretes 1000 to 2000 ml of urine daily. The volume and concentration of urine is controlled by: – Antidiuretic hormone(ADH) – Mineralocorticoids – The Renin – angiotensin mechanism

Urination