ACB 406.3 Lecture Notes - Lecture 9: Germinal Matrix, Melanin, Dermal Bone

• School: U of S
• Department: Anatomy and Cell Biology
• Course: ACB 406.3
• Professor: Helen Nichol

Document Summary

During fetal development, mesenchymal cells populate the skin mesenchyme interact w/ epithelium to form hair placodes growth influenced by hormones: hair placode = small epidermal invaginations (wnt signaling) Hair papilla = it is dermis w/ a little capillary loop: o(cid:374) top the(cid:396)e(cid:859)s a (cid:271)asal la(cid:373)i(cid:374)a where division occurs cells move up and die to make up the hair shaft. Basement membrane - called a glassy membrane: everything outside is the dermis, anything inside is epidermally-derived. Layers of the hair: external and internal root sheath: central = medulla, outer = cortex, thin layer outside = cuticle. Melanocytes lie in the stratum basale above the hair papilla: passes melanosomes upward to keratinocytes that form the cortex of the hair and gives color to the hair. The hair root (bulb) b is in the hypodermis (subcutis) Most follicles are seen in oblique section. It is genetically programmed for hair to die hair cycle: animals would shed their fur color depending on the season.