L8: Skin Flashcards
What are the types of skin?
β Thick (non-hairy) skin: found in palms and soles.
β Thin (hairy) skin: covers the rest of the body.
What are the layers of skin?
β Epidermis: Stratified squamous keratinized epithelium.
β Dermis: Connective tissue.
N.B: The hypodermis is the subcutaneous adipose tissue (It is not a part of the skin).
What is the structure of thin skin?
formed of two layers
1) Epidermis: Contains 4 types of cells: (KMβL)
ο² keratinocytes (85% of cells).
ο² Langerhans cells.
ο² Melanocytes.
ο² Merkel cells.
2) Dermis: (PR)
ο² Papillary layer
ο² Reticular layer
How many layers are keratinocytes arranged in?
4
Malpighian layer (2 layers) - stratum basale and stratum spinosum
Granular layer (Skin Barrier layer) - stratum granulosom
Clear layer - stratum lucidum
Horny cell layer - stratum corneum
Characters of the basal cell layer in the skin
S: Single layer of columnar cells.
N: Nucleus: basal & oval.
C: Cytoplasm: deep basophilic& (due to ribosomes).
E: By EM: It contains prekeratin filaments.
F: Function: Responsible for regeneration of keratinocytes so it shows mitotic figures.
Characters of a prickle cell layer in the skin
L: L/M: Formed of 4-8 cell layers.
S: Shape: polyhedral.
N: Nuclei: Central and rounded.
C: Cytoplasm: pale basophilic.
E: EM: The cells are connected by cytoplasmic processes. (Desmosome)
Characters of the granular layer in the skin
S: Shape: 2- 4 layers of flattened, diamond-shaped cells.
N: nuclei: flat & central.
C: Cytoplasm: has basophilic Keratohyaline-granules.
E: EM: The cytoplasm contains βlamellar granulesβ, which
contain phospholipids
F: Function: The granules are released in the intercellular
space to act as skin barrier because they are:
ο² waterproofing skin.
ο² preventing foreign bodies from penetrating the skin.
What are the characteristics of the clear layer of the skin?
ο It appears as a (CHAT W) thin, wavy, clear, homogenous acidophilic line.
ο It is formed of dead non-nucleated flattened cells, βscalesβ which contain βeleidin granulesβ (derivative of kerato- hyaline granules).
What are the characteristics of the horny cell layer in the skin?
ο It consists of several layers of (AHS) acidophilic horny scales called βsquamesβ
ο The scales contain soft keratin (derived from eleidin).
ο The squames are continuously shed or sloughed from the surface and continuously replaced by new ones from the deeper cells.
What is the site of melanocytes?
between the cells of the basal layer of the epidermis.
What is the LM of melanocytes?
S: shape: branched cells with rounded cell bodies
N: Nucleus: rounded and central
C: Cytoplasm: contains melanin pigment (brown to black
pigment, responsible for pigmentation of the skin).
What is the function of melanocytes?
synthesis of melanin
What are the clinical applications of melanocytes?
Albinism
What is albinism and what is its cause?
- an inherited disease characterized by white hair and very light-colored skin.
- Cause: Albinism is caused by a mutation in genes responsible for melanin formation.
What is the site of langerhans cells ?
upper layers of Spinouts layer.
What is the origin of Langerhans cells?
blood monocytes.
What is the LM on Langerhans cells?
S: Shape: branched.
N: Nucleus: central.
C: Contain Birbeck granules.
Stained with silver& vital stains.
What is the function of Langerhans cells?
Phagocytic& antigen-presenting cells (APC).
What is the site of Merkels cells?
Basal cell layer of epidermis.
What is the function of Merkels cells?
Receptors for touch sensation.
Compare between the papillary layer and the reticular layer of the dermis
What are the histological differences between thin and thick skin?
What are skin related structures?
β They include:
ο² Sweat glands.
ο² Hair& hair follicle.
ο² Sebaceous glands.
ο² Arrector pili muscle.
What is the site of sweat glands?
deep in the dermis or the hypodermis.
What is the number of sweat glands?
more numerous in the thick skin than in the thin skin.
What are the types of sweat glands? And compare between them.
What is the structure of sweat glands?
1) The secretory parts (acini)
2) The Excretory parts (ducts)
- Duct collects sweat secretion from the acini
- In merocrine glands: duct ascends in a spiral course to the epidermis
- It opens on the surface of the skin.
What does the hair consist of (by naked eye)?
Shaft: projecting above skin surface.
Root: embedded or implanted in the skin.
Hair bulb:
β’ the expanded lower end of the hair.
β’ It consists of (hair matrix) which is a cellular mass.
β’ Proliferation of the matrix cells results in growth of the hair in length.
What does the shaft of the root of the hair consist of?
Medulla: It contains soft keratin.
Cortex: It contains hard keratin and melanin pigments which give the color of the hair.
Cuticle: It contains hard keratin.
What is the definition of hair follicles?
It is a hole formed by an epidermal down-growth in which the root of the hair is present.
What is the structure of hair follicles?
The wall of the hair follicle is called (root sheath) which is divided into 3 types:
Inner root sheath: ββββ
Outer root sheath: It is identical with the malpighian layer of the epidermis.
CT Sheath: It is a condensed part of C. T. of the dermis.
What is the site of sebaceous glands?
They open into the upper 1/3 of the hair follicle at the obtuse angle between the follicle and the surface of the skin
What is the mood of secretion of Sebaceous glands?
Holocrine
i.e. the central cells disintegrate completely to secrete (sebum).
What is the mood of secretion of Sebaceous glands?
Holocrine
i.e. the central cells disintegrate completely to secrete (sebum).
What is the structure of sebaceous glands?
- Secretory part: It is a sac-like structure i.e formed of one or more alveoli which open into a common duct.
- Excretory duct: Short, wide and opens into the upper 1/3 of the hair follicle, Lined with stratified squamous epithelium.
What is the definition of arrector pili muscles?
β It is a band of smooth muscle fibers touching the bottom of the sebaceous gland.
What is the function of the arrector pili muscles?
β Contraction of this muscle due to stress or emotion (as fear) leads to:
ο² Erection of the hair shaft.
ο² Appearance of goose-skin.
ο² Squeezing of sebaceous secretion into the duct
