Structure and functions of organs in urinary system-1

Because it removes waste from the blood and expels it from the body, the urinary system is also known as the excretory system of the body. The kidneys are responsible for producing urine, while the other organs in the system handle its transportation, short-term storage, and removal.

The urinary system includes:

• Two kidneys 
• Two ureters 
• One urinary bladder 
• One urethra

Functions of the Urinary System

• Controlling blood volume through excretion or water conservation.
• Urine production, elimination of urine, other waste products, and medications from the body.
• Regulating the body's acid-base balance.
• The making of hormones (renin, erythropoietin and calcitriol).

Kidney

External Structure of the Kidney

The kidneys are bean-shaped organs that are situated one on either side of the spinal column in the posterior wall of the abdominal cavity. The kidneys are situated between the third lumbar vertebra and the twelfth thoracic vertebra (T12 to L3). The right kidney is slightly lower than the left because of the space the liver takes up. An area of fat called perirenal fat holds them in place.

Adult kidneys measure 12 cm in length, 5 to 7 cm in width, and 3 cm in thickness. Male kidneys weigh 150 g, whereas female kidneys weigh 130 g. The color of the kidneys is a deep red. The last pair of ribs and the adrenal gland serve as partial protection for them. The kidney has lateral convexity and medial concavity. The hilus (a little indentation area) on the medial concave edge is where the ureters, nerves, and blood arteries enter and exit the kidney. The superior pole of the kidney, where the adrenal gland is located, and the inferior pole.

The kidneys are surrounded by three layers of connective tissue:

• Renal Capsule
  • The kidney is shielded from injury and infection by its innermost, transparent, fibrous tissue.
• Adipose Capsule or Perinephric Fat
  • Fatty tissue in the middle layer, which holds the kidney against the posterior wall and shields it from injury.
• Renal Fascia
  • The kidney is anchored to the surrounding structures and to the abdominal wall by its outer fibrous connective tissue.
• Pararenal Fat or Paranephric Fat
  • The lumbar region's extraperitoneal fat is what is most noticeable posterior to the kidney. Collagen bundles are sent through the para-nephric fat by the renal fascia.

Organs Associated to the Kidney

 Anterior Relation

Numerous structures are connected to the anterior surface of the right kidney, some of which are situated next to the kidney and others of which are separated from it by a layer of peritoneum:

• The right suprarenal gland covers a tiny portion of the superior pole.
• The remainder of the upper portion of the anterior surface is next to the liver and is separated from it by a layer of peritoneum as we move inferiorly.
• The retroperitoneal, descending portion of the duodenum contacts the kidney in the middle. On its medial side, a section of the intraperitoneal small intestine covers the inferior pole of the kidney, which is directly connected to the right colic flexure on its lateral side.

Numerous structures are connected to the anterior surface of the left kidney, some directly against the kidney and some with a layer of peritoneum in between:

• The left suprarenal gland is located on the medial side of the superior pole and covers a little portion of it.
• The intraperitoneal stomach and spleen cover the remainder of the superior pole.
• The center portion of the kidney is covered by the retroperitoneal pancreas, which is moving inferiorly.
• The left colic flexure and the beginning of the descending colon cover the lower half of the kidney on its lateral side, and the intraperitoneal jejunum portions cover the lower half of the kidney on its medial side.

Posterior Relation

• The left and right kidneys are connected to comparable tissues in the back. The diaphragm is located above, and the psoas major, quadrates lumborum, and transversus abdominis muscles are located under it, from medial to lateral.
• While the same region of the left kidney is prior to ribs XI and XII, the superior pole of the right kidney is anterior to rib XII. As a result, the costodiaphragmatic recesses and pleural sacs extend posteriorly to the kidneys.
• The iliohypogastric and ilio-inguinal nerves, as well as the subcostal vessels and nerves, pass posterior to the kidneys as well.

Internal Structure of the Kidney

The cortex and the medulla are two distinct regions that make up the kidney's interior.

• The Cortex
  • The outermost part of the kidney, which is light red in color, is called the renal cortex. The outer cortical and the inner juxtamedullary areas make up this structure. Renal columns are made of cortical tissue that extends between pyramids. Collecting tubules make up the majority of the renal columns.
• The Medulla
  • The inner, reddish-brown, darker region of the kidney is called the medulla. It is made up of 8 to 18 renal pyramids, which are clusters of collecting ducts in the shape of cones. The outer cortex is next to the base of each pyramid. Each renal pyramid has a "papilla" at its tip, which opens to a "minor calyx." The nephron's tubules and collecting ducts are found in pyramids. A main calyx is the drain for several lesser calyces. There are between 8 and 18 minor calyces and 1-2 major calyces. The renal pelvis is filled with the urine that is continuously drained from the papillae by the calyces.

The upper portion of the ureters, which expand at the hilus, form the kidney's large collecting space, or renal pelvis. The ureter then carries the urine to the bladder after it has passed through the renal pelvis.

Blood Supply of the Kidney

• The right and left renal arteries, which are the branches of the abdominal aorta, amply supply the kidneys with arterial blood. The renal artery splits into multiple arteries that nourish various parts of the kidney inside the kidney. The renal artery initially separates into a number of segmental arteries, then into interlobar arteries, which are further divided into the arcuate arteries. Arcuate artery divisions result in a network of interlobular arteries, which sprout afferent arterioles as their offshoots. 20 to 25 percent of the cardiac supply goes to the kidneys. The renal vein, which transports blood to the inferior vena cava, drains the venous blood.

Nerve Supply of the Kidney

• The sympathetic component of the autonomic nervous system supplies the kidneys with nerves.