Skin and mucous membranes Flashcards
Functions of the skin
Protection (pathogens, UV, injury), thermoregulation (blood vessels, hair, sweat), water regulation, sensation, absorption, storage and synthesis (vit D)
Layers of the skin
epidermis, dermis, subcutis/ subcutaneous layer
What are sebaceous glands?
Found in hair follicles, secrete sebum
Basic structure of the epidermis
Keratinised stratified, squamous epithelium. No capillaries and no nerve endings.
Layers of the epidermis
Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum in thick skin, stratum corneum.
What is stratum basale?
Basal cell layer. One cell remains and acts as a stem cell that divides to form epithelial cells.
What is stratum spinosum?
Prickle cell layer. Cells have desmosomes
Desmosomes function
attach epithelial cells to each other
What is stratum granulosum?
Granular cell layer. Cells become smaller and fatter and accumulate keratohyaline granules. The nucleus degenerates and disappears.
What is stratum corneum?
Keratin
Which epidermis cell layer is only visible in thick skin?
Stratum lucidum (clear cell layer). Between stratum granulosum and stratum corneum. Pale waxy appearance with no nucleus.
Name of cells that produce keratin
Keratinocytes (95% of epidermal cells)
Name and features of antigen presenting cells found in the epidermis
Langerhans cells. Have dendritic cell projections from cell body
Name and location of sensory receptors
Merkel cells found underneath basal cell layer
Function and location of melanocytes
produce melanin and found in stratum basale
How to identify melanocytes in specimen
Tend to be paler in colour. No desmosomes. Shrinking of cells gives appearance of clear space around melanocytes
Difference between thick and thin skin
Thick skin has stratum lucidum, thicker stratum corneum, more prominent stratum granulosum (more keratin granules).
Location of thick skin
Palms of hands and soles of feet. Areas of fingers (e.g. where pen is held)
Dermis description
strong flexible connective tissue layer rich in collagen (mostly) and elastic fibres
location of dermis
beneath epithelium/epidermis
What are fibroblasts?
Thin spindle shaped cells that produce collagen. Found in dermis
Contents of dermis
fibroblasts, macrophages, adipocytes, nerve endings, blood vessels, smooth muscle, lymphatic vessels, glands, hair follicles
2 layers of dermis
Papillary layer and reticular layer
What are rete / epidermal ridges?
Papillary layer has upward projections while epithelial layers of epidermis have downward projections. Hold epidermis and dermis tightly together.
Description of papillary layer
Has rete ridges. Richly supplied with capillaries and nerve endings
Description of reticular layer
Dense connective tissue containing blood vessels and lots of fibres
Causes of acne
overproduction of sebum from sebaceous glands, infections from bacteria on skin, hormones, diet (fat), smoking
What is psoriasis?
Autoimmune condition that primarily affects skin
Feature of psoriasis in oral cavity
lesion on tongue
cause of psoriasis
rapid turnover of epidermis cells (7 instead of 28 days) which causes a thicker epidermis. Blood in underlying capillaries due to inflammation
Signs of psoriasis
Red, scaly patches typically on scalp ad areas of friction (knees and elbows)
What is Pemphigus vulgaris?
Autoimmune condition that affects skin and mucous membranes
Sign of pemphigus vulgaris
Blisters on skin and oral cavity. May look like raw, painful areas of mouth due to blisters rupturing very quickly.
How do blisters form in Pemphigus vulgaris?
Autoantibodies attack desmoglein (protein that forms desmosomes) which breaks up attachment of epithelial cells. Spaces form between epithelial cells which become filled with fluid - blisters.
How do lesions impact the water regulating ability of the skin?
Loss of fluid can occur from lesions -> dehydrations
What drug can be used to bring pemphigus vulgaris into reemission
corticosteroids
What is vitiligo?
Autoimmune condition that causes loss of skin pigment - autoantibodies formed against melanocytes or melanocyte-stimulating hormone.
two commonest skin cancers
squamous cell carcinoma (malignancy of epithelial cells), basal cell carcinoma
What is skin cancer?
Uncontrolled growth of epithelial cells that creates lump that breaks down to create a crusty, scaly area of skin with a red, inflamed base
One of most dangerous skin malignancy
Malignant melanomas
risk factors for malignant melanomas
UV radiation, moles (collection of melanocytes), fair skin with freckles, sunburn, family history
What are mucous membranes?
specialised epithelial lining which produced a lubricant fluid (mucous) containing mucin (sticky protein)
Function of mucous membranes
defence mechanism, protective, secretory (stomach can produce gastric enzymes and acid), absorptive (small intestine), sensation
Structure of mucous membranes
Contains 2 layers - epithelial and lamina propria (mucosae) separated by basement membrane
What cell type makes up the epithelial layer in mucous membranes?
Stratified squamous epithelia
What is the lamina propria?
A supportive areolar layer (loose fibrous CT) beneath the mucosal epithelium and its basement membrane.
What makes up the lamina propria mucosae?
Cells (fibroblasts, immune cells, lymph nodules), extracellular matrix (ground substance, collagen, elastin fibres)
Example: cells that make up the trachea
pseudostratified ciliated columnar epithelium and goblet cells. Lamina propria under epithelium
Example: composition of small intestine
absorptive epithelium with a brush border, goblet cells that produce mucin, villi containing lots of lymphatics
Functions of the oral mucosa
Protection, sensation (touch, pain, taste), secretion (salivary glands), permeability and absorption (rapid drug delivery)
Composition of oral mucosa
stratified squamous epithelium, lamina propria
3 types of mucous membrane in mouth
lining, masticatory, gustatory
Structure and location of lining mucous membrane
non-keratinised stratified squamous epithelium. red tissue. Buccal, floor of mouth, soft palate
Structure and location of masticatory mucous membrane lining
thick layer of keratin. present in areas of trauma from food - gingiva, hard palate and tongue
Composition and location of gustatory mucous membrane
taste buds. tongue
How can keratinised tissue be divided microscopically?
orthokeratosis (pure keratin, no nuclei) or parakeratosis (remains of nuclei - little dark dots)
Congenital meaning
present from birth
What is lichen planus?
A rash that can affect skin and mucous membranes. Painless or stinging/burning sensation
Cause of cystic fibrosis
Autosomal recessive condition causes a mutation in CFTCR gene (cystic fibrosis transmembrane conductive regulator gene)
Effects of cystic fibrosis
thick and stagnated mucous affects the epithelial lining of the respiratory, gastrointestinal and reproductive tracts, and salivary glands (prone to calcification and inflammation). Site for invasion of pathogens (respiratory tract infections)
