Integumentary System Flashcards
Pilosebaceous apparatus
Hair
Sebeceous Glands
Arrector pili muscle
Skin
Epidermis
Dermis
Hypodermis under skin
Functions of skin
Protection Permeability barrier Thermoregulation Sensation Metabolic functions Immunologic defense Sexual attractant
Developmental Sources of skin
- Epidermis from ectoderm
- Demis from Mesoderm
(in back from dermatomes and in Abdomen and limbs from parietal Mesoderm)
Epidermis
Stratifies squamous keratinized that produces protein keratin
Cells of epidermis
keratinocytes
Melanocytes
Langerhans cells
Merkel cells
Cellular layers of Epidermis in thin skin
basal layer
spinous cell layer
Granular layer
Keratin layer
all layers are composed of keratinocytes
Basal layer
- single layer of cuboidal cells
- divide and are responsible for Regeneration
- each cell is Bound to b.m. by hemidesmosomes
- cells are conencted by desmosomes
- keratinocytes contain tonofilaments
Spinous cell layer
- polyhedral keratinocytes
- Synthesis of tonfilaments continues
- tonofilaments converge into the desmosomes
Granular layer
- cells are flatter
- contain keratoyalin adn membrane Coating granules
Membrane- Coating granules
- in granular layer cells
- contain Lipids
- secreted by exocytosis into intercellular spaces
- responsible for Formation of epidermal water barrier
Keratohyalin granules
- in granular layer cells
- contain intermediate Filament- associated proteins
- released into keratinocyte cytoplasm
- filaggrin and trichohyalin promote Aggregation of tonofilaments into tonofibrils –> initiaton the production of keratinization
Keratin layer
- no nuclei
- flakes of keratin
- coated with anti-wetting agents
- breakdown of nucleus and other organelles
- thickening of Plasma membrane
pH decreases
Epidermal water barrier
two structural Elements:
1. Lipid envelope of anti-wetting agents
2- Cell envelope with insoluble proteins on inner Surface of Plasma membrane
Epidermis of thin skin
Clear layer between granular layer and keratin layer
Deep epithelial ridges and ling dermal papillae
Clear layer
in thick Skin
eosinophilic cells full of eleidin
Skin Color depends on
Melanin
Red blood cells in dermal vascular beds
Carotenes
Bilirubin
Melanin
Eumelanin (yellowish Brown to black)
Pheomelanin: pink to red blue
Melanocytes
- in basal layer
- from neural crest
- round with numerous processes
- contain promelanosomes and melanosomes –> Synthesis of Melanin
- Melanin is produced from tyrosine
Langerhans cells
- in all layers except keratin layer
- lobulated nucleus
- cytoplasmic processes
- present Antigens to T-lymphocytes
- derived from monocytes
Merkel cells
- in basal layer
- rounded, branchd
- contain vesicles
- make synaptic Connection with sensory nerve
- intra-epidermal touch receptors!!!
Epithelial ridges and dermal papillae
epithelial downsgrowths
dermal outgrowth
Dermis
CT blood and lymphatic vessels, nerves hair follicles sebaceous Glands arrector pili muscles Sweat glands
Layers of dermis
Papillary layer (superficial) Reticular layer (deeper)
Papillary layer of dermis
loose CT with type I and III collagen
Reticular layer of dermis
dense irregular CT with type I Collagen and elastic fibers
Hypodermis
loose CT and adipose tissue
for Energy storage and insulation
Nerve supply of skin
free nerve endings
Meissner’s coupuscles: in dermal papillae, touch receptors
Pacinian corpuscles: in deeper dermis and hypodermis, detect pressure
Ruffini’s corpuscles: Respons to mechanical displacement
Hair (parts)
Hair follicle
hair shaft
hair follicle
3 Segments
1- infundibulum (until Opening ob sebaceous Gland)
2- Isthmus: until arrector pili muscle
3- Inferior Segment with hair bulb
5 layers: inner three: shaft, outer two: sheaths
External root sheath
basal layer of Epithelium continiuation
separated by surrounding CT by glassy membrane
Internal root sheath
- cells whihc become lighlty keratinized and disintegrate at Level of sebacous gland
Hair shaft structure
Medulla (moderate keratinization)
Cortex (highly keratinized, contains Pigment)
Cuticle (contains overlapping keratin plates)
Hair color
Melanocytes are in Matrix in Cortex
Melanin is in cells of cortex
Sebaceous glands
- surround hair follicles
- branched acinar
- sebum onto hair shaft
- short duct is called pilosebaceous canal
- sebum is product of holocrine secretion
Arrector pili muscle
smooth msucle
one end in follicle and the other into papillary layer of dermis
surrounds sebaceous gland
Contraction of arrector pili muscle results in:
hair rises
sebum is discharged
goose skin
Types of Sweat glands
eccrine and apocrine
Eccrine Sweat glands
- almost everywhere (mostly in Palms and soles)
- Secretory Portion is tubular and coiled in reticular layer
- clear and dark cells
- secretory mode is eccrine
coiled duct has stratified cuboidal epithelium
Apocrine Sweat glands
- large Glands in axillae and genital regions
- Deep in hypodermis
- secrete into adjacent hair follicle via duct
- secretory Portion is tubular and coiled and has cuboidal and myoepithelial cells
- secretion is eccrine!!!
Fingernail
- nail bed is stratified squamous
- nail root in dermis
- growth: Proliferation, differntiation, keratinizationof Epithelium –> nail Matrix
- lunula at base of nail
- Eponychium: Skin overlying the root
- Hyponyhcium: Skin beneath free end of nail
Breast (mammary Gland)
Compund tubular
during lactation (tubule-acinar)
12-25 lobes
Development of mammary gland
6th to 7th week: ectodermal thickening –> two mammary lines
small Portion in thoracic Region invaginates into Underlying Mesenchyme –> lactiferous ducts
Stroma in mammary gland
Interlobular stroma: dense irregular CT and adipose tissue
Intralobular stroma:loose, more cellular and less fibrous CT
Changes in mammary gland
inactive Gland: undifferentiated ducts, no alveoli, simple cuboidal, interlobular dense CT, adipose CT
Active Gland: Differentaition of alveoli
Active lactating Gland: Secretion of milk, simple columanr, thin Septa, adipose CT
Secretion of milk
Merocrine for proteins
Apocrine for droplets
in first few days after birth: alveoli begin to secrete a protein-rich fluid called COLOSTRUM
production is controlld by prolactin
Lactiferous ducts
15-25 ducts each draining into one of the lobes
within nipple: duct is dilated to form lactiferous Sinus
lined by stratified epithelium
myoepithelail cells in mammary gland
surround alveoli and ducts
contract under Oxytocin and help to discharge the milk
