BIS104 Note17

BIS104 Note17 - Lecture 17 Bio Sci 104 Development...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 17 1 Bio Sci 104 Winter 2010 Development (continued) XI. What about events controlling differentiation at the tissue level, both in embryogenesis and in the adult after embryogenesis is complete? A. Each organ is a mix of different cell types, each contributing its own function. Where do these different specialized cells originate during embryogenesis? 1. Often, the "ancillary" cells originate outside of the organ itself, and invade it during organogenesis. 2. For example: limbs first form primarily of epithelial and mesodermal tissue by a budding process described in the previous lecture. Muscle cells for limb, however, originate in somites flanking spinal column, and migrate into developing limb buds, divide, differentiate, and made appropriate contacts with developing bones. Similarly, neuronal axons originating in the spinal cord invade the developing limbs, and made appropriate contacts with new muscle cells. At least part of migration regulated by cell-cell and cell- extracellular matrix communications. Deve lop ing b lood vesse ls are a lso induced to invade limb tissue (angiogenesis) in response to clues released by limb cells. Neural crest cells enter limb to differentiate into efferent nerve cells, and to form melanocytes (pigment cells). B. In adult, replicative and relatively undifferentiated stem cells can generate new differentiated cells to replace those lost through wear and tear; however, not all populations of cells in the adult do this; some tissues and organs are formed during embryogenesis and are retained throughout adult life: no replication occurs and these cells cannot be replaced when damaged. Examples include nerve cells, heart muscle cells, auditory hair cells, and lens cells of eye (note that nerve cell axons, if cut, can partially re-grow, but this depends on neuron body not being damaged). This does not mean that these permanent cells do not repair themselves, just that they do not replicate in adult life: Retinal photoreceptor cells do not replicate in adult, but continually replace the membrane discs of photosensitive rhodopsin . Heart cells don't replicate in adult, but replace macromolecules as they wear out. C. In contrast to above, however, many of the differentiated cell populations in the adult are not permanent, but instead are continually dying and being replaced. This can occur through simple duplication (i.e. replication with no change in differentiation state), or by
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Lecture 17 2 where the terminally differentiated state cannot self-replicate and must be replaced from a relatively undifferentiated pool. Examples include epidermis and blood cells. IX. Tissues with cells that replicate in adult life
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/15/2010 for the course BIS 104 taught by Professor Scholey during the Fall '08 term at UC Davis.

Page1 / 8

BIS104 Note17 - Lecture 17 Bio Sci 104 Development...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online