Understanding the Longitudinal Section (L.S.) of the Kidney

The kidney is a vital organ in the human excretory system, responsible for filtering blood, removing waste, and maintaining fluid and electrolyte balance. A longitudinal section (L.S.) is a cut along the length of the kidney, revealing its internal structure. Let's break down the labeled parts step by step:

Step 1: Outer Cortex

The outermost region is the cortex. It appears granular and contains renal corpuscles (glomeruli and Bowman's capsules) and convoluted tubules where initial blood filtration occurs.

Step 2: Inner Medulla

Beneath the cortex lies the medulla, which is divided into conical masses called renal pyramids. The pyramids appear striated due to the presence of collecting ducts and loops of Henle, which concentrate urine.

Step 3: Renal Columns

Extensions of the cortex between the pyramids are called renal columns (or columns of Bertin). They contain blood vessels and provide structural support.

Step 4: Renal Pelvis

The innermost region is the renal pelvis, a funnel-shaped space that collects urine from the pyramids via calyces (minor and major calyces). The pelvis leads to the ureter.

Step 5: Hilum

The hilum is a notch on the concave side of the kidney where the ureter, renal artery, and renal vein enter or exit.

Step 6: Ureter

The ureter is a tube that carries urine from the renal pelvis to the bladder.

Final Labeled Diagram (Conceptual)

In a typical L.S. diagram, you would label: Cortex, Medulla, Renal Pyramid, Renal Column, Renal Pelvis, Calyx, Hilum, and Ureter.

Related Topics

Nephron Structure: The functional unit of the kidney, located in the cortex and medulla, involved in filtration, reabsorption, and secretion.

Urine Formation: Processes including glomerular filtration, tubular reabsorption, and tubular secretion occur in the nephron.

Excretory System: Overview of kidneys, ureters, bladder, and urethra in waste elimination and homeostasis.

Key Formulae (Related to Kidney Function)

Glomerular Filtration Rate (GFR): $GFR = \frac{U \times V}{P}$ , where U is urine concentration, V is urine flow rate, and P is plasma concentration of a substance like creatinine.

Net Filtration Pressure (NFP): $NFP = P_{GC} - P_{BC} - π_{GC}$ , where P_GC is glomerular capillary pressure, P_BC is Bowman's capsule pressure, and π_GC is blood colloidal osmotic pressure.