Intro to Histology Flashcards
What does epithelial tissue do?
serves as a lining or covering
Main functions of epithelial tissue
Protection, transport, secretion/excretion, absorption
Epithelial tissue characteristics
cell-cell junctions, functional polarity (top and bottom), basement membrane (basal ECM produced by epithelial cells)
What are the types of cell-cell junctions?
tight junctions, anchoring junctions, desmosomes, hemi-desmosomes, and gap junctions
Where are tight junctions on the cell and what is their function?
Just below the apical surface of the cell on the lateral border
they prevent anything from coming further down the cell surface into the tissue underneath
Where are adhering junctions on the cell and what is their function?
Go around the entire perimeter of the cell wall
stick the cell wall to the adjacent cell wall to increase structural integrity and to communicate w the external environment
Where are desmosomes and what is their function?
They are spots of adhesion that connect to other cell desmosomes via proteins called cadherins
Where are hemidesmosomes and what is their function?
Attach the basement membrane (basal ECM) to the basal part of the cell via integrins
What are gap junctions?
low resistance junctions that form a channel from one cell to the adjacent cells
How are different types of epithelium classified?
of layers and the shape of the apical layer
number of epithelial layers descriptors
Simple, pseudostratified, stratified
different epithelial shape descriptors
Squamous, columnar, cuboidal, transitional
How many layers are in simple epithelium and what kinds of shapes can it have?
one cell layer thick
squamous (nucleus squished & compressed), cuboidal (nucleus dead center), and columnar (nuclei closest to bottom)
How many layers are in pseudostratified epithelium and what kinds of shapes can it have?
one cell layer thick
not all cells reach the surface, but they all touch the bottom
How many layers are in stratified epithelium and what kinds of shapes can it have?
two or more layers
cuboidal and columnar are rare
stratified squamous can help anywhere there is a lot of wear and tear
Integument main functions:
protection against antigens and utilized for immunity
homeostasis (prevents water loss)
sensation
metabolic functions
Three layers of integument:
epidermis, dermis and subcutaneous layers
Name the five layers of the epidermis
stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum
what are keratinocyes?
cells in epithelium that produce keratin
what is keratin?
fibrous substance and protein that can withstand tensile stress
What three cell types can be found in the Stratum Basale layer of the epidermis?
stem cells, melanocytes (produce melanin), and Merkel cells (sensory receptor cells)
What are the main cells in the stratum spinosum and what is their function?
Langerhans cells aka prickle cells
First part of immune response; produced in bone marrow and migrate to skin (take antigen and remove it from epidermis)
They also have many desmosomes to weld to the adjacent membrane for constant abrasion and stabilization
What’s going on in the stratum granulosum?
keratohyalin granules (keratin accumulation)
loss of nuclei
lamellar bodies (extrude waxy substance that waterproofs the skin)
cells connect to each other w/ tight junctions to prevent things going deeper/things from escaping
Stratum lucidum
only in thick skin
transition zone from nuclei to none
Stratum corneum
shredding keratin/dead skin cells
What are the two layers of the dermis?
Papillary layer and Reticular layer
What are the three things in the papillary layer of the dermis?
Dermal papillae (increase mechanical stability b/w the dermal and epidermal layers)
Meissener’s corpuscles (spiraled sensory organs)
Fibroblasts (wound healing)
What is in the reticular layer of the dermis?
lymphatic vessels (where langherin cells deposit antigens sebaceous glands
What’s in the subcutaneous layer?
Loose CT (adipose tissue: fat tissue, insulation) Pacinian corpuscles (Sensitive to deep pressure and vibration) sweat glands (stem cells)
What are free nerve endings and where are they located?
Lack coating of CT and are sensitive to pain and temperature
located in the epidermis
What are Merkel’s cells and where are they located?
They are in the Stratum basale layer of the epidermis and are sensory receptor cells that are sensitive to touch (tactile)
What are Meissner’s corpuscles and where are they located?
They are located in dermal papilla and they are tacticle
What are Pacinian corpuscles and where are they located?
They are located in the Hypodermis and are sensitive to deep pressure and vibration
What are Ruffini’s corpuscles and where are they located?
They are located in the Dermis and are sensitive to stretching
