Dr. Malik Zohaib Ali

General and Systemic Anatomy

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Urinary System

• It removes wastes from the body.

• It also maintains homeostasis or a constant internal

environment within the body.

Components of Urinary System

• The urinary system consists of two kidneys, two ureters, the

urinary bladder and the urethra.

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Kidney

• A pair of excretory organs

• Dark brown in color

• Situated with the dorsal wall of the abdominal cavity on each

side of the aorta and caudal vena cava, just ventral to the first

few lumber vertebrae.

• Function

• They remove the waste products of metabolism and excess of

water and salts from the blood and maintains its pH.

Urinary System3

Conti…

• Retroperitoneal Organ

• The kidneys are described as retroperitoneal because they

are partly surrounded by fat and are covered only on their

ventral surface by peritoneum.

• Borders

1. Lateral border (convex)

2. Medial border (straight)

• Surfaces

1. Dorsal

2. Ventral

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Right Kidney

• Location

• It lies opposite the first three lumbar vertebrae. It is farther

cranial than the left kidney by the length of half a kidney.

• Relation

• It is more extensively related to the liver than to any other

organ. Its cranial third is covered by caudate lobe of the liver.

• The remaining ventral surface is related to duodenum, the

right lobe of the pancreas, the cecum and the colon.

• The caudal vena cava is on the medial border of the right

kidney.

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Conti…

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Left Kidney

• Location

• The left kidney lies opposite the second, third and fourth

lumbar vertebrae.

• Relation

• It is related ventrally to the colon and the small intestine.

• The spleen is related to the cranial extremity of the kidney.

• The medial border is close to the aorta.

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Gross Features

• Cortex: it is the peripheral part of the renal parenchyma. It

contains the renal corpuscles and convoluted portion of the

tubules.

• Medulla: It is centrally located dense parenchyma of the

kidney. It gives striated appearance due to presence of

numerous collecting ducts in this region.

• Cortico-medullary Junction: it is formed by the joining part

of the cortex and medulla.

• Renal capsule: it is the outermost strong fibrous covering of

the kidney.

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Conti…

• Hilus: it is an indention present at the middle of the medial

border of the kidney, where the renal vessels and nerves and

the ureter communicate with the organ.

• Renal Pelvis: it is the expanded portion of the ureter within

the kidney.

• Renal Sinus: it is the fat-filled space that contains the vessels

and surrounds renal pelvis.

• Renal Pyramid: it is formed by the medulla portion of the

kidney; It is also triangular in outline.

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Conti…

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Conti…

• Renal Crest: The longitudinal ridge projecting into the renal

pelvis is the renal crest, through which collecting tubules of

the kidney excrete urine into the renal pelvis.

• Arcuate branches: The vessels that are apparent at the

cortico-medullary junction are the arcuate branches of the

renal vessels.

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Blood Supply

• Because of its important role in adjusting the composition of

extracellular fluid (including plasma), the blood supply to the

kidney is much more extensive than the size of the organ would

suggest. The two renal arteries may receive as much as one

fourth of the total cardiac output.

• Each renal artery enters the hilus of the kidney and divides into

a number of relatively large branches, the interlobar arteries.

These pass peripherally between pyramids almost to cortex,

where they bend abruptly and become arcuate arteries, which

derived their name from the arched manner by which they

pass along the junction between cortex and medulla.

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Conti…

• The arcuate veins drain blood from both the cortex and

medulla, pass through the medulla as interlobar veins, and

enter the renal veins, which emerge from the renal hilus to

empty into the caudal vena cava.

• Nerve supply

• Sympathetic nerves are the primary innervation of the

kidneys.

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Ureters

• A pair of narrow, thick walled muscular tubes which convey urine

from the kidneys to the urinary bladder.

• The ureter begins at the renal pelvis and terminates at the

urinary bladder.

• The smooth muscle of the ureter undergoes peristaltic waves of

contraction that encourage the flow of urine to the urinary

bladder.

• Divisions

• (i) Abdominal part of ureter

• (ii) Pelvic part of ureter

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Urinary Bladder

• It is a long, narrow pisiform mass which acts as a temporary

store house of urine which gets emptied through the urethra.

• The detrusor muscle of urinary bladder is arranged in whorls and spirals and is adapted for mass contraction rather than peristalsis.

• Location

• When empty, it lies on the floor of the pelvic inlet.

• When distended, it lies on the floor of the abdomen and

conforms in shape to the caudal part of the abdominal cavity

because it displaces all freely movable viscera. It frequently

reaches a transverse plane through the umbilicus.

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Conti…

• Parts

(i) Vertex: It is the anterior blind part.

(ii) Body: It is the middle rounded part of the bladder.

(iii) Neck: It is the posterior narrower extremity that joins the

urethra.

• Ligaments

• It is fixed in position by the two types of ligaments.

(i) Lateral ligament; two in numbers

(ii) Medial ligaments

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Urethra

• The urethra is a tube extending from the urinary bladder to the

outside of the body.

• Male urethra

• The male urethra subserving the functions of urination and

ejaculation i.e. expulsion of semen.

• Female urethra

• The female urethra is for urination only.

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THE END

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