In: Biology
Describe the external structure of the kidney?
internal structure, draw a diagram of the longitudinal section
through the kidney and label the structures ?
The kidneys are two bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about 12 centimetres (4.7 in) in length. They receive blood from the paired renal arteries; blood exits into the paired renal veins.
External Anatomy
The paired kidneys lie on either side of the spine in the
retroperitoneal space between the parietal peritoneum and the
posterior abdominal wall, well protected by muscle, fat, and ribs.
The left kidney is located at about the T12 to L3 vertebrae,
whereas the right is lower due to slight displacement by the liver.
Upper portions of the kidneys are somewhat protected by the
eleventh and twelfth ribs. Each kidney weighs about 125–175 g in
males and 115–155 g in females. They are about 11–14 cm in length,
6 cm wide, and 4 cm thick, and are directly covered by a fibrous
capsule composed of dense, irregular connective tissue that helps
to hold their shape and protect them. This capsule is covered by a
shock-absorbing layer of adipose tissue called the renal fat pad,
which in turn is encompassed by a tough renal fascia. The fascia
and, to a lesser extent, the overlying peritoneum serve to firmly
anchor the kidneys to the posterior abdominal wall in a
retroperitoneal position.
Each kidney looks like the kidney bean and the renal hilum is the
entry and exit site for structures servicing the kidneys: vessels,
nerves, lymphatics, and ureters. The medial-facing hila are tucked
into the convex indentation of the kidney.
Internal Anatomy
A frontal section through the kidney reveals an outer region called
the renal cortex and an inner region called the renal medulla. In
the medulla, 5-8 renal pyramids are separated by connective tissue
renal columns. Each pyramid creates urine and terminates into a
renal papilla. Each renal papilla drains into a collecting pool
called a minor calyx; several minor calyces connect to form a major
calyx; all major calyces connect to the single renal pelvis which
connects to the ureter.