Renal Tubules and Collecting Duct

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Questions and Answers

What is the main function of the brush border in the proximal tubule?

To increase the rate of absorption from the lumen into the cell (correct)

To regulate the pH of the tubular fluid

To facilitate the transport of sodium ions

To increase the rate of secretion from the cell into the lumen

What is the primary function of the Na+ K+ ATPase enzyme in the proximal tubule?

To regulate the pH of the tubular fluid

To facilitate the transport of water and ions

To engage in active transport of ions (correct)

To increase the surface area of the basolateral cell membrane

What is the term for the process of engulfing water and molecules in the proximal tubule?

Endocytosis

Exocytosis

Pinocytosis (correct)

Phagocytosis

What is the function of the tight junctions in the proximal tubule?

To seal the intercellular space from the tubule's lumen Signup and view all the answers

What is the name of the portion of the proximal tubule that is present in the medulla?

Pars recta Signup and view all the answers

What is the characteristic feature of the cytoplasm of proximal tubule cells in H&E stained sections?

Eosinophilic (acidophilic) Signup and view all the answers

What is the name of the part of the renal tubule that starts at the urinary pole of Bowman's capsule?

Proximal tubule Signup and view all the answers

What is the term for the in-foldings of the basolateral cell membrane in the proximal tubule?

Infoldings Signup and view all the answers

What is the primary function of the proximal tubule?

Reabsorbing 70% of water and electrolytes Signup and view all the answers

What is the characteristic of the epithelium lining the thin segments of the descending and ascending limbs of Henle's loop?

Simple squamous epithelium Signup and view all the answers

What is the primary function of the thick ascending limb of Henle's loop?

Sodium chloride active transport Signup and view all the answers

What is the name of the structure that is divided into three parts: straight part, distal convoluted tubule, and connecting tubule?

Distal tubule Signup and view all the answers

What is the characteristic of the basal cell membrane infoldings in the proximal tubule?

Creates basal cell compartments with abundant mitochondria Signup and view all the answers

What type of Henle's loop is present in the juxtamedullary nephron?

Long-looped Henle's tubule Signup and view all the answers

What is the primary function of the loop of Henle?

Water retention to produce hypertonic urine Signup and view all the answers

What is the characteristic of the epithelium lining the thick segment of the descending limb of Henle's loop?

Simple cuboidal epithelium Signup and view all the answers

Study Notes

The Renal Tubule

The renal tubule consists of three parts: the proximal tubule, the loop of Henle, and the distal tubule.

The Proximal Tubule (PT)

Occupies most of the cortical renal tissue
Begins at the urinary pole of Bowman's capsule
Divided into two regions: convoluted portion (proximal convoluted tubule; PCT) and straight portion (pars recta)
Histological features:
- Simple cuboidal epithelium with dense eosinophilic (acidophilic) cytoplasm and basal round nuclei
- Apical cell membrane has a densely packed microvilli forming a brush border
Ultrastructural features:
- Apical brush border with pinocytotic vesicles and canaliculi
- Basolateral cell membranes with Na+ K+ ATPase enzyme and infoldings for active ion transport
- Lateral cell membranes with interdigitations, making boundaries indistinguishable by light microscope
Function:
- Obligatory reabsorption of 70% of water and electrolytes, vitamins, glucose, and proteins from the glomerular filtrate

The Loop of Henle

Classified into three types based on length of segments: short-looped, intermediate, and long-looped
Histological features:
- Thick segment of the descending limb: simple cuboidal epithelium
- Thin segments of the descending and ascending limbs: simple squamous epithelium
- Thick segment of the ascending limb: low cuboidal epithelium
Function:
- Water retention to produce hypertonic urine and maintain body water
- Thin descending limb is permeable to water, while the ascending limb is impermeable
- Sodium chloride is actively transported out of the tubule in the thick ascending limb

The Distal Tubule (DT)

Divided into three parts: straight part, convoluted part, and macula densa

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Description

Learn about the structure and functions of the renal tubules, including the proximal tubule, loop of Henle, and distal tubule, and their role in the kidney's filtering process.