For learning anatomy, please visit :
My youtube channel : @easyhumanatomy73
My website : http://easyhumananatomy.com
My facebook page: https://www.facebook.com/easyhumanatomy/
My blog: http://www.easyhumanatomy73.blogspot.com
My blog: Difference between : http://www.microscopicanatomybd.blogspot.com
Epidermis of skin : microscopic and clinical anatomy
Skin : It
has two layers
1.
Epidermis
2.
Dermis
Sometimes, hypodermis consider as third layer of skin contain subcutaneous
fat.
Epidermis
It is the superficial layer of skin which is formed
by keratinized stratified squamous epithelium.
Cells of epidermis: It is composed of
four cell types:
1.
Keratinocytes,
2.
Melanocytes,
3.
Langerhans cells, and
4.
Merkel cells.
The keratinocytes are arranged in five layers, and the
remaining three cell types are interspersed between them .
Five
layers of the epidermis: deep to superficial
1. Stratum Basale :
A
single layer of cuboidal to columnar cells that stand on the basement membrane.
This is a region of cell division.
It also
contains melanocytes and Merkel cells.
2. Stratum Spinosum: it is composed by many layers of polyhedral prickle cells
bearing intercellular bridges. Mitotic activity is also present.
It also
contains Langerhans cells and processes
of melanocytes.
3. Stratum Granulosum : it is composed by flattened cells which contain keratohyalin
granules.
It is absent as a distinct layer in thin
skin.
4. Stratum Lucidum A thin, translucent
layer that is also absent in thin skin.
5. Stratum Corneum it is composed of squamous
cells packed with keratin. Superfi cial squamous cells are desquamated.
Location of skin cells and functions
Difference between location, functions & development
of different skin cells
|
Cells of skin |
Location |
Functions |
Development |
|
Keratinocytes
|
New skin cells
develop at the bottom layer of your epidermis
(stratum basale) and travel up through the other layers as
they get older. |
It forms barrier
against environmental damage by heat, UV radiation, dehydration, pathogenic
bacteria, fungi, parasites, and viruses. |
Surface ectoderm |
|
Melanocytes
|
Stratum
basale |
Melanocytes
are well known for their role in skin pigmentation, and their ability
to produce and distribute melanin has been studied extensively |
Neural crest |
|
Langerhans
cells |
Stratum
spinosum |
These
cells act as the outermost guard of the cutaneous immune system and are
likely to induce the first reactions against pathogens encountered via the
skin |
Fetal
Langerhans cells from Primitive yolk sac in fetal life , in adult Langerhans cells
from fetal monocytes |
|
Merkel
cells |
Stratum
basale |
It
is also known as tactile epithelial cells, which is an oval-shaped mechanoreceptors essential
for light touch sensation |
Surface
ectoderm |
Keratinocytes, reach
the outermost layer of your epidermis after about a month, where the skin cells
shed from your body as new cells develop at the bottom layer.
Albinism
It is
a congenital disorder characterized by the complete or partial absence of melanin
pigmentation in the skin, hair, iris of
eye, and eyelashes.
It is an autosomal recessive/X
-linked disorder.
Although the melanocytes are present,
but genetic mutation results in lack of tyrosinase enzyme, which catalyzes the
production of melanin from tyrosine.
People with albinism
have skin that is very sensitive to light and sun. Sunburn is one
of the most serious complications of albinism.
This allows light to
shine through the irises and makes the eyes extremely sensitive to bright light.
Vitiligo
It is s a clinical condition with presence of spots without
melanin in the skin, which occurs due to partial or complete absence of
melanocytes.
