Transcellular transport C can be

active or passive. Electrogenic Na+ transport plays a central role as the driving force behind many absorptive processes. Na+ is pumped into the intercellular space by a Na+ pump located at the basolateral cell membrane. This process is ATP-dependent and creates an extreme difference between the Na+ concentration inside the cells (15 mmol/l) and the plasma (140 mmol/ l). Additionally, this creates a potential difference of about -40 mV between the two media.

On the lumen side, the enterocytes are connected by tight junctions. Particularly in the proximal regions of the small intestine, though, the latter are sufficiently permeable to allow para-cellular diffusion along a concentration gradient. This can occur in both directions so that water and electrolytes, e. g., can also reach the lumen. Even small particles are able to pass through the apparently dense intestinal mucosa by translocation (leaky gut). These intact, undigested particles play an important role, for instance, in triggering allergic reactions.

- A. Villus with Brush Border

Paneth's granular cells Stem cells

Nutrient flow

Goblet cells

Goblet cells

Planaria Nervous System Diagram

Basal membrane x Capillary-

Nutrient flow

mi

Brush border mimnnrn

Abso

rption

"y

Basal membrane x Capillary-

B. Enterocyte Histology

Microvillus

Central microfilament

Microvillus

Central microfilament

Cellulardiffusion

Mitochondrion

Hemidesmo-somes

Basal lamina

Mitochondrion

Hemidesmo-somes

Basal lamina

Transcellular transport

Transcellular transport

Intercellular communication

— Microvilli

Paracellular diffusion Translocation

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Responses

  • Jessika
    Which intercellular connections force transcellular transport to occur?
    6 years ago

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