Summary of Radiation Effects on Tissues and Organs
Radiation Effects on Tissues and Organs: A Student Guide
Introduction
The kidneys are paired, bean-shaped organs that filter blood, remove waste, and help maintain fluid and electrolyte balance. This material breaks kidney anatomy into clear sections so you can study independently and efficiently.
Definition: The kidneys are retroperitoneal organs that filter blood to form urine, regulate blood pressure, electrolyte balance, and acid-base homeostasis.
External Anatomy
Location and surface features
- The kidneys lie in the retroperitoneal space, usually between the levels of the T12 and L3 vertebrae.
- Each kidney is about 10–12 cm long in adults and has a convex lateral surface and a concave medial border.
- The medial border contains the renal hilum where structures enter and leave: the renal artery, renal vein, and ureter (from posterior to anterior: vein, artery, pelvis/ureter).
Surrounding structures
- Superiorly: adrenal (suprarenal) gland sits on top of each kidney.
- Anteriorly: right kidney — liver; left kidney — spleen, stomach, pancreas.
- Posteriorly: muscles of the posterior abdominal wall and ribs provide protection.
Definition: The renal hilum is the entry/exit site on the medial kidney border for vessels, nerves, lymphatics, and the ureter.
Internal Anatomy
Gross internal divisions
- Cortex: outer region containing renal corpuscles and convoluted tubules.
- Medulla: inner region organized into renal pyramids; pyramids end at papillae that drain into minor calyces.
- Pelvis: funnel-shaped dilated proximal part of the ureter collecting urine from major calyces.
Table: Cortex vs Medulla
| Feature | Cortex | Medulla |
|---|---|---|
| Main components | Glomeruli, proximal and distal convoluted tubules | Loops of Henle, collecting ducts, renal pyramids |
| Function emphasis | Filtration and reabsorption start | Concentration of urine, water and salt balance |
| Appearance | Granular | Striated (due to parallel ducts) |
Nephron — functional unit
- Each kidney contains about 0.8–1.5 million nephrons.
- Nephron components:
- Renal corpuscle: glomerulus (capillary tuft) + Bowman's capsule.
- Proximal convoluted tubule (PCT)
- Loop of Henle (descending and ascending limbs)
- Distal convoluted tubule (DCT)
- Collecting duct (collects urine from multiple nephrons)
Definition: A nephron is the microscopic structural and functional unit of the kidney that filters blood and produces urine.
Practical sequence of filtrate flow:
- Blood enters glomerulus via afferent arteriole.
- Filtrate collects in Bowman's space.
- Filtrate passes through PCT, loop of Henle, DCT.
- Several DCTs drain into a common collecting duct, which empties at the papilla into a minor calyx.
Blood Supply and Innervation
- Renal artery branches from abdominal aorta; renal vein drains into inferior vena cava.
- Segmental → interlobar → arcuate → interlobular arteries supply renal tissue.
- Nephron blood flow: afferent arteriole → glomerular capillaries → efferent arteriole → peritubular capillaries or vasa recta.
Table: Arterial branching
| Level | Typical order |
|---|---|
| Main renal artery | Branches into segmental arteries |
| Segmental | Interlobar arteries along columns |
| Interlobar | Arcuate arteries at cortico-medullary junction |
| Arcuate | Interlobular arteries into cortex |
- Innervation: sympathetic fibers adjust renal blood flow and renin release; parasympathetic influence is minimal.
Definition: The vasa recta are straight capillaries in the medulla that maintain the osmotic gradient necessary for urine concentration.
Filtration and Functional Zones (Conceptual)
- Cortex: where most filtration and reabsorption occur (glomeruli, PCT, DCT).
- Outer medulla: active salt transport in thick ascending limb.
- Inner medulla: high osmolarity environment; urea recycling and water reabsorption occur along collecting ducts.
Practical example: Concentrating urine
- When antidiuretic hormone (ADH) is present, collecting du
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Kidney Anatomy Basics
Klíčová slova: Radiation effects, Tissue classification, Kidney anatomy, Liver histology
Klíčové pojmy: Kidneys are retroperitoneal organs that filter blood and regulate homeostasis., Renal hilum contains renal vein, renal artery, and ureter (from anterior to posterior: vein, artery, pelvis/ureter)., Cortex contains glomeruli and convoluted tubules; medulla contains loops of Henle and collecting ducts., A nephron consists of glomerulus, PCT, loop of Henle, DCT, and collecting duct., Blood flows: afferent arteriole → glomerular capillaries → efferent arteriole → peritubular capillaries or vasa recta., Arterial branching: renal → segmental → interlobar → arcuate → interlobular arteries., Loop diuretics act on the thick ascending limb; thiazides act on the DCT; collecting duct is affected by aldosterone and ADH., ADH increases water permeability of collecting ducts to concentrate urine., Hydronephrosis results from urinary obstruction causing dilation of pelvis and calyces., Kidneys receive ~20%–25% of cardiac output, highlighting their filtration role.