Questions and Answers
What type of epithelium lines the upper part of the female urethra?
Transitional epithelium
What is the length of the female urethra?
4-5 cm
Which gland opens in the course of the male urethra?
The male urethra is approximately 20 cm long.
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Which part of the male urethra is lined by transitional epithelium?
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The muscular layer of the bladder consists of _____ muscle fibers.
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What type of muscle forms the external sphincter around the urethra?
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What is the lamina propria of the urethra composed of?
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What is the main function of the urinary system?
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Each kidney contains between 1 and 3 million nephrons.
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What is the shape of each kidney?
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The renal pelvis is divided into _ major calyces.
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What type of connective tissue surrounds each kidney?
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What is the primary function of the juxtaglomerular cells?
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The proximal convoluted tubule has a wide diameter.
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Which layer of the ureter is composed of smooth muscle?
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What primarily happens to urine in the collecting tubules?
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The structure that covers the glomerulus is called _
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Match the following nephron structures with their functions:
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Study Notes
Overview of the Urinary System
- Involved in urine formation, waste removal, hormone production, and fluid and electrolyte balance.
- Comprises two kidneys, two ureters, a urinary bladder, and a urethra.
Kidneys
- Primary excretory organs, each measuring approximately 11cm x 5cm x 2cm.
- Enclosed by a tough connective tissue capsule and surrounded by perirenal fat for support.
- Features a medial concave border (hilum) leading to the renal sinus, housing renal vessels, lymphatics, nerves, and renal pelvis.
- Renal pelvis branches into 2-3 major calyces, further divided into 2-3 minor calyces.
- Kidney structure includes an outer cortex (granular) and inner medulla (striated), with medullary pyramids projecting into the cortex.
Histological Structure of the Kidney
- Stroma: Covered with fibrous connective tissue, minimal connective tissue around blood vessels.
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Parenchyma: Composed of uriniferous tubules, which are highly vascular.
- Nephrons produce urine.
- Collecting tubules concentrate urine.
Nephrons
- Each kidney hosts 1-3 million nephrons, with multiple nephrons draining into single collecting tubules.
- Nephron structure includes:
- Malpighian corpuscle (renal corpuscle)
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
Malpighian Corpuscle
- Located in the cortex, consists of:
- Glomerulus: A network of capillaries from afferent arterioles with fenestrated endothelium and thick basement membrane.
- Bowman’s Capsule: Two-layered, enclosing the glomerulus, with an outer parietal layer and inner visceral layer (podocytes).
- Podocytes play a vital role in forming the blood-renal barrier, crucial for glomerular filtrate formation.
Proximal Convoluted Tubule
- Begins at the urinary pole of the renal corpuscle and is highly convoluted.
- Lined with pyramidal cells exhibiting a brush border and acidophilic properties.
- Key functions include reabsorption of sodium, water, glucose, amino acids, and low molecular weight proteins.
Loop of Henle
- U-shaped segment consisting of:
- Thick descending limb (similar to PCT)
- Thin descending limb (permeable to water)
- Thin ascending limb (permeable to sodium)
- Thick ascending limb (impermeable to water)
Distal Convoluted Tubules
- Continuation of the thick ascending loop, joining collecting tubules.
- Characterized by wider lumen and cuboidal cells with distinct boundaries.
- Responsible for sodium and water reabsorption under hormonal control (aldosterone and ADH).
Juxtaglomerular Apparatus
- Comprises juxtaglomerular cells, macula densa, and extraglomerular mesangial cells.
- Juxtaglomerular cells secrete renin affecting blood pressure regulation and erythropoietin for RBC production.
- Macula densa senses chloride ions, influencing glomerular filtration rate.
Collecting Tubules
- Begin at the medullary rays, leading into the medullary pyramids and forming the duct of Bellini.
- Lined with simple cuboidal to columnar epithelium.
- Function to reabsorb water under ADH influence, concentrating urine prior to renal calyces.
Ureters
- Extends from renal pelvis to the urinary bladder, with a stellate lumen.
- Histological features include:
- Mucosa: Transitional epithelium and dense connective tissue.
- Muscular layer: Smooth muscle arranged in inner longitudinal and outer circular layers.
- Adventitia: Fibroelastic connective tissue.
Urinary Bladder
- Thick-walled, expandable organ with a transitional epithelial lining.
- Histological structure includes:
- Mucosa: Transitional epithelium with pliable layers.
- Muscular layer: Thick smooth muscle fibers.
- Adventitia: Dense connective tissue, covered by peritoneum.
Urethra
- Female Urethra: Short (4-5 cm), lined with transitional and stratified squamous non-keratinized epithelium, featuring an external sphincter for micturition control.
- Male Urethra: Longer (approximately 20 cm), conducting urine and seminal fluid, with associated glands.### Urethra Structure Overview
- The urethra comprises three main segments: prostatic urethra, membranous urethra, and penile urethra.
Prostatic Urethra
- Located within the prostate gland.
- Lined by transitional epithelium, allowing for flexibility.
- Features an internal elevation that projects into the lumen.
- Ejaculatory ducts open laterally from the elevation.
Membranous Urethra
- Lined by a combination of stratified epithelium and pseudostratified columnar epithelium.
- It is the shortest segment of the urethra.
Penile Urethra
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Comprises two distinct parts:
Bulbous Urethra
- Traverses the corpus spongiosum tissue.
- Lined by pseudostratified or stratified columnar epithelium.
Pendulous Urethra
- Extends through the glans penis, dilating to form the fossa navicularis.
- Primarily lined by stratified squamous epithelium, providing protection.
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Description
Explore the essentials of human histology focusing on the urinary system in Chapter 5. Learn about urine formation, waste removal, hormone production, and the regulation of fluid balance. This quiz covers the anatomy of the kidneys, ureters, bladder, and urethra.
