9/4b Integument Histology Flashcards
All of the cells in the body are classified into 4 different tissue types?
YES
- epithelial
- connective
- nervous
- muscle
Epithelial tissue
serves as the external layer of the body or the layer lining something (layer that lines all blood vessels). MOST Superficial layer
Avascular
What are the main functions of epithelial tissue?
Protection - from UV rays
Transport - across cell membranes
Secretion/Excretion - secretes inactive form of vitamin D and excretes salt from sweat glands
Absorption - epithelium lines various segments of intestines
Main characteristics of epithelial tissue?
Cell-Cell Junctions
Functional Polarity
Connected to a basement membrane
What are the different kinds of cell-cell junctions in epithelial tissue?
Tight/occluding junctions
Adhering/anchoring junctions (not restricted to epithelial)
Communicating (gap)
What is a tight/occluding cell-cell junction in epithelial tissue?
lateral border and just superficial to the cell surface. Prevent anything from entering the cell.
Ex: Blood Brain Barrier in the brain. Only certain things are allowed to get through the cells and nothing is between the cells
What are the different kinds of adhering/anchoring cell-cell junctions in epithelial tissue?
Desmosomes
Hemi-desmosomes
Zonula Adherens
What is a communicating (gap) cell-cell junction in epithelial tissue?
low resistance junction, connection of proteins that form a channel and allows for easy passage from one cell to an adjacent cell (not only epithelial)
Desmosomes
Adhering/anchoring cell-cell junction of epithelial tissue
- Spot weld, like a dot of glue
- Connected with intermediate filaments (have the ability to resist tensile stress)
- Connected to intermediate filaments via cadherins
- Aid in structural integrity of the cell
- Communicate with external environment
Hemi-desmosomes
Adhering/anchoring cell-cell junction of epithelial tissue
- half interacts with the cell
- other half interacts with the basement membrane
- connected with proteins called integrins to basement membrane/basal lamina
Basement membrane of epithelial adhering cell
special layer of ECM that anchors the epithelium to whatever is underneath it
difference between basal lamina and basement membrane of a cell?
NONE
Integrins
proteins that connect the cytoskeleton and the ECM (extracellular matrix)
Zonula Adherens
Adhering/anchoring cell-cell junction of epithelial tissue
- Follows the perimeter of the cell wall, often called belt adhesion.
- sticks the cell wall to an adjacent cell wall
- helps increase structural integrity
- helps communicate with the external environment
what is the significance of the functional polarity characteristic of epithelial tissue?
- it defines the top and bottom of all epithelial cells
- allows things to go through the epithelial tissue in a distinct pathway
- apical surface faces the lumen
lumen
center
apical
at the top
How is epithelium classified?
- Number of layers
- Shape
What are the differnt layers of epithelium
Simple - 1 cell layer, squamous cuboidal columnar
Pseudostratified - 1 cell layer, not all cells reach the surface, all cells touch the bottom and adhere to basement membrane, columnar
Stratified - 2 or more layers, squamous cuboidal columnar, High Keratin and Moderate Keratin
What are the different shapes of epithelium
squamous - fat in the middle and thin on the outside
cuboidal - all sides are the same size
columnar - rectangular, long sides
transitional - only seen in the bladder, not a focus
Main function of stratified squamous??***
either highly keratinized or moderately keratinized and it helps anywhere where there is a lot of wear and tear.
Ex - vocal cords, trachea, and any place where there is a lot of mechanical stress
Functions of integument
Protection - barrier and immune
Homeostasis - body temp and water loss
Sensation - sends sensory info to CNS
Metabolic Function - secretes precursor to vitamin D and excretes salt from sweat
Structure of integument
Epidermis (5 layers) - top
Dermis (2 layers) - middle
Hypodermis - base
Structure of the epidermis of integument
4-5 layers
- B - stratum basal (B)/germanativum (bottom most layer)
- S - stratum spinosum
- GR - stratum granulosum
- L - stratum lucidum
- C - stratum coreum
Epidermis
4-5 layers
highly keratinized
major cell type - keratinocyte
Keratinocyte
starts as a stem cell at the base of the epidermis and migrates over around a month to the top most layer at the cell surface
Stratum basal (B)/germinativum
- bottom-most layer
- faces the dermis
- 1 cell layer thick
- made of stem cells (precursor for keratinocytes), melanocytes (produce skin pigment), and merkel cells (sensory receptors that are tactile)
stratum spinosum
- prickle cells/pieces of Velcro (second from the bottom)
- Spot welds used as junctions because skin has constant abrasion
- creates stability
- desmosome are the connecting welds
- langerhans cells - detect antigens in epidermis and migrate out
langerhans cells
- part of the stratum spinosum(second from the bottom layer of the epidermis)
- detect antigens that enter the epidermis
- produced in bone marrow
- take foreign substance and migrate out of epidermis
Stratum granulosum
- small dots that produce lamellar bodies (3rd from the bottom)
- produce and accumulate keratin in the granules of the keratinocytes
- loose nuclei
- extrude a waxy-like substance from the cells that aids in water-proofing and hydration
- connected by tight junctions
Stratum lucidum
- clear layer (4th from the bottom)
- transition zone from having nuclei to no nuclei
- only seen in thick skin
stratum corneum
shedding skin (top most layer)
Layers of the dermis
Papillary layer
Reticular layer
Papillary layer*****
- layer of the dermis
- dermal papillae increase mechanical stability holding the epidermis to the dermal layer
- Meissner’s corpuscle - (compact fluorescent bulb), tactile sensory organ*****
- Role of fibroblast - WOUND HEALING
Reticular layer
- layer of the dermis
- has lymphatic vessels, hair follicles and sebaceous glands (epidermal derivatives)
- when langerhans (in stratum spinosum) ID foreign bodies, they send to the reticular layer of the dermis
hypodermis
Fat cells (primarily) Blood vessels Glands pacinican corpuscle nerves
purpose of fat cells in the hypodermis
regulate body temp
start spanning the reticular layer of the dermis too
what does the pacinian corpuscle do?
it is a sensory corpuscle and detects deep pressure and vibration
Integument nerve supply
- free nerve endings: in E layer, respond to pain and temperature, don’t have CT around them
- merkel’s cells: tactile in nature, E layer
- meissner’s corpuscle: papillary dermis, tactile in nature
- pacinian corpuscle: hypodermis, deep pressure and vibration
- ruffini’s corpuscle: dermis, sensitive to stretch
