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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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