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Histology of Integumentary
System
By
Dr. Mudassar Ali Roomi (MBBS, M.Phil.)
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Histology of Integumentary
System
By
Dr. Mudassar Ali Roomi (MBBS, M.Phil.)
7/31/2019 2nd Lecture on the Histology of Skin by Dr. Roomi
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CELLS OF EPIDERMIS
Keratinocytes are the
predominant cell type
Non-keratincytes
include:
1. melanocytes
2. Langerhans cells
3. Merkel cells.
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1. Melanocytes
The color of the skin is the result
of several factors:
1. keratinocytes' content of melanin
2. carotene3. number of blood vessels in the
dermis.
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1. Melanocytes (cont..)
melanin is a brownish black pigment
produced by the melanocyte
Melanocytes are neural crest
derivatives***
Location: These cells are present inthe stratum basale**
They have rounded cell bodies and
form hemidesmosomes with the
basal lamina, but no desmosomes
with adjacent keratinocytes.
Long irregular dendritic extensions
from each melanocyte branch into
the epidermis, running between the
cells of the basal and spinous layers
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2. Dendritic (Langerhans)
Cells (cont)
These are antigen-presenting
cells (APCs)
Location: usually seen in spinous
layer.
Cytoplasmic processes extend
from these cells between
keratinocytes of all the layers.
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2. Dendritic
(Langerhans) Cells
Function:
They are bone marrowderivedcells, capable of binding,processing, and presentingantigens to T lymphocytes in thesame manner as macrophages inother organs do
microorganisms cannotpenetrate the epidermis withoutalerting its dendritic cells andtriggering an immune response.
Langerhans cells, along withlymphocytes of skin make up amajor component of the skin'sadaptive immunity.
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3. Tactile (Merkel) Cells
These are mechanoreceptors thatresemble keratinocytes withkeratin filaments in theircytoplasm
Small, Golgi-derived dense-coreneurosecretory granules are
present in their cytoplasm. Derived from neural crest cells
Merkel cells are located in thebasal epidermal layer in areas ofhigh tactile sensitivity
The basolateral surfaces of the
cells contact expanded terminaldiscs of unmyelinated sensoryfibers that penetrate the basallamina.
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Thick and thin skin
These are distinguished on the basis ofthe
thickness of the epidermis
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Thick skin
Epidermis= 400-600 um thick
Has got a prominent st.corneum, a well developed st.granulosum and a distinct st.lucidum
Location: It lines the palms ofhands and the soles of feet
It lacks hair follicles,sebaceous glands and arrectorpili muscle.
Contains greater number ofsensory receptors and eccrinesweat glands than thin skin.
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Thin skin
Epidermis= 75-150 um thick
Less prominent st. corneumand generally lacks st.granulosum and st. lucidum.
Location: Thin skin coversmost of the parts of thebody
It contains hair follicles,sebaceous glands andarrector pili muscles.
It contains less number ofsensory receptors andeccrine sweat glands thanthick skin.
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