Q.Sketch and label 'L.S. of human kidney'.

Columns of Bertin are cortical extensions found between the medullary pyramids of the kidney.

In a longitudinal section (L.S.) of a mammalian kidney, the kidney is differentiated into an outer cortex and an inner medulla. The medulla is not uniform — it is organised into a number of conical masses called medullary (renal) pyramids, with their broad bases towards the cortex and their apices (papillae) projecting into the minor calyces.

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Columns of Bertin are cortical projections that extend between the renal (medullary) pyramids.

Internally the kidney has an outer cortex and an inner medulla. The medulla is divided into conical masses called medullary pyramids.

The cortical substance is not confined to the outer region alone; it sends inward extensions in between adjacent medullary pyramids.

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One renal artery brings blood into the kidney; one renal vein carries the filtered blood out.

Each kidney is supplied and drained by a single major vessel on its medial (concave) side, at the hilum/hilus:

• Renal artery — a short, wide branch that arises directly from the abdominal aorta and enters the kidney at the hilum. It carries oxygenated blood loaded with nitrogenous wastes (urea, uric acid, etc.) into the kidney to be filtered by the nephrons. Inside the kidney it branches progressively into interlobar, arcuate, interlobular arteries and finally into the afferent arterioles that supply each glomerulus. …

Each kidney is supplied by a renal artery (blood entering) and drained by a renal vein (blood leaving).

Each kidney receives blood from a renal artery, which is a direct branch of the abdominal aorta. The renal artery enters the kidney at the hilum (hilus), a notch on its concave medial border, and divides into smaller arteries and afferent arterioles that supply the glomeruli of the nephrons for filtration.

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Renal pyramids are the medullary tissue masses of the kidney, and the renal papilla is the tip of each pyramid through which urine drains into the calyx.

Each human kidney is divided into an outer cortex and an inner medulla. The medulla is not uniform but is organised into a number of conical/triangular striated structures called renal (medullary) pyramids, consisting mainly of the loops of Henle and collecting ducts of the nephrons, along with the vasa recta.

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Retroperitoneal organs are abdominal organs positioned behind the peritoneal lining rather than inside the peritoneal cavity, attached directly to the posterior body wall.

Most abdominal organs (like the stomach, liver, and much of the intestine) are enclosed within the peritoneum and suspended from the body wall by mesenteries, sitting essentially inside the peritoneal cavity. Retroperitoneal organs, by contrast, lie behind (dorsal to) the peritoneum, sandwiched between the parietal peritoneum and the posterior (dorsal) abdominal wall, and are covered by peritoneum on only their front surface, not all around.

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Columns of Bertin are cortical-tissue extensions found between the medullary pyramids of the kidney.

Each human kidney, in longitudinal section, shows an outer region called the cortex and an inner region called the medulla. The medulla is not uniform — it is divided into 8–12 conical masses called the medullary pyramids, whose broad bases face the cortex and whose apices (papillae) project into the minor calyces.

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Renal columns (columns of Bertin) are cortex-derived tissue wedged between the medullary pyramids of the kidney.

In a longitudinal section of the human kidney, the outer region is the cortex and the inner region is the medulla, which is divided into 8–10 conical masses called the medullary/renal pyramids, with their broad bases towards the cortex and apices (papillae) opening into the minor calyces.

Between any two adjacent pyramids, tissue of the cortex extends downward, penetrating into the medulla. These wedge-shaped extensions of cortical tissue lying between the pyramids are called the columns of Bertin (renal columns).

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Columns of Bertin are cortical tissue extensions that dip between the renal pyramids of the kidney medulla.

Each human kidney is divided internally into an outer cortex and an inner medulla. The medulla is not a single continuous mass but is organised into 8-12 conical structures called renal (Malpighian) pyramids, with their broad bases facing the cortex and their apices (papillae) opening into the minor calyces.

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Retroperitoneal organs lie outside/behind the peritoneal lining, fixed against the back wall of the abdomen.

The abdominal cavity is lined by a double-layered serous membrane, the peritoneum (a parietal layer lining the wall, and a visceral layer covering organs). Most digestive organs (stomach, most of the intestines, liver, spleen) are 'intraperitoneal' — fully wrapped in peritoneum and suspended by mesentery. In contrast, some organs develop and remain behind the parietal peritoneum, attached directly to the posterior body wall; these are called retroperitoneal organs. This group classically includes the kidneys and ureters, the adrenal (suprarenal) glands, most of the pancreas, and parts of the duodenum and l …

Columns of Bertin are cortical tissue projecting between the medullary pyramids; the Duct of Bellini is the large collecting duct opening at the papilla of a pyramid.

The internal structure of the human kidney, covered in the Excretory Products and their Elimination chapter of NCERT Class 11 Biology, shows an outer cortex and an inner medulla organised into renal pyramids. The two named structures are distinguished as follows: