Proximal convoluted tubule, aka, PCT.
- Bulging cuboidal/low columnar cells
- Basal membrane has infoldings with their own mitochondria.
- Microvilli that make up the brush border that fills the lumen; give the lumen a characteristic "fuzzy" appearance.
- The basal membrane infoldings and brush border increase the surface area for diffusion; approximately 65% of reabsorption and secretion occurs within the PCT.
- Lateral processes are cytoplasmic extensions that form lateral intercellular space; held together by intercellular junctions.
- Large roundish euchromatic nucleus
- It has several light-staining areas of euchromatin that reflect genome activity; know that the the dark-staining areas are heterochromatin, which comprises transcriptionally inactive portions of the genome.
- Abundant mitochondria, which produce visible basal striations; mitochondria support the energetic requirements of the sodium-potassium pump, which plays a key role in resorption of water and nutrients from the PCT.
- Abundance of dark-staining organelles, including the vesicles and mitochondria, give PCT cells a darker hue.
Distal convoluted tubule
- Cuboidal and uniform cells
- Lateral processes and intercellular junctions
- Basal membrane infoldings
- Luminal surface does not have a brush border, so the lumen appears wider and clearer than the PCT.
- Euchromatic nuclei that they tend to lie close to the lumen, even bulging into it.
- Numerous mitochondria and vesicles to support their high cellular activity, though not as much as the PCT; hence, these cells appear lighter in histological samples.
- Macula densa is a tightly packed region of the DCT that lies near the renal corpuscle and afferent arteriole of the nephron.