Intro to Histology (9/4b) Flashcards
4 Basic Tissue Types
Epithelial
Connective
Nervous
Muscle
Epithelial Tissue - Description
Superficially lines almost everywhere in the body
Avascular
Cell-cell junctions
Functional polarity
Basement membrane
Epithelial Tissue - Functions
Protection (EX: against UV rays and antigens)
Transport (EX: across cell membrane)
Secretion/excretion (EX: secretes vit D, excretes salt)
Absorption (EX: GI tract)
3 main functions of cell-cell junctions
Barrier
Structural
Communication
3 main types of cell-cell junctions
Occluding/Tight junctions
Adhering/Anchoring junctions
Communicating/Gap junctions
Occluding/Tight junction
some things can get through but nothing can get between the functions
(EX: blood brain barrier)
Communicating/Gap junction
connection of proteins that forms a channel, relays a message to the next cell as it gets stretched or compressed
3 Types of Adhering junctions
Desmosomes
Hemidesmosomes
Zonula adherens
Desmosomes (adhering junction)
a spot on the cell membrane that adheres, intermediate filaments connect one desmosome to another
IFs attach desmosome to adjacent cell desmosome via cadherins
Cytoskeleton of a cell and exterior of the adjacent cell
Hemidesmosomes (adhering junction)
has part of desmosome on cell membrane side but not the other, and it interacts with basal lamina
Attach to the ECM via integrins
Zonula adherens (adhering junction)
runs along the width of the cell wall surface like a belt, sticking one cell wall to the adjacent cell wall
Basal lamina (basement membrane)
a basal ECM secreted by epithelial cells
Comprised of laminin and collagen
Attached to basal surface of epithelia by hemidesmosomes
Helps epithelium adhere to underlying tissue
Functional polarity
has apical and basal surfaces that have polarity
Apical = faces lumen/external surface
Basal = faces ECM
Apical layer types
Simple
Pseudostratified
Stratified
Simple cell layer
Thickness: 1 layer
Shapes: simple-squamous, cuboidal, columnar
Pseudostratified cell layer
Thickness: 1 layer, all cells touch basal lamina but not all reach apical surface
Shapes: pseudostratified columnar
Stratified cell layer
Thickness: 2+ layers
Shapes: stratified squamous (highly or moderately keratinized) [ex: vocal cord, or any place where there is a lot of wear and tear], cuboidal/columnar
Cell shapes
Squamous
Cuboidal (cubic, top/bottoms same size)
Columnar (tall/thin, small tops and bottom with longer lateral)
Transitional
Integument (skin) - Function
Protection (barrier/immune)
Homeostasis
Sensation
Metabolic functions
Integument - 3 Layers
Epidermis (top)
Dermis (middle)
Hypodermis (bottom)
Epidermis (epithelium) - Description
4 strata in thin skin, 5 strata in thick skin
Avascular
Keratinocytes are the main cells
Has keratin (filamentous, aids in withstanding tensile stress)
Avascular
receives nutrition from outside of itself
Epidermis - Layers
(Top → Bottom) Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale
Epidermis - Stratum corneum (C)
Keratinocytes shed keratin - layer is highly keratinized
Epidermis - Stratum lucidum (L)
only in thick skin
transition from where cells have nuclei to where they don’t
Epidermis - Stratum granulosum (G)
Keratohyalin granules (arrows) - accumulating keratin
Loss of nuclei - essentially dead
tight junctions to prevent water loss
HAS: Lamellar bodies, tight junctions
Melanocytes
produce skin pigment
Merkel cells
tactile sensory receptor cells for light touch
Langerhan’s cells
first part of immune response
detects antigens that have managed to get into the skin and takes them to lymph tissue
produced in bone marrow
Lamellar bodies
aids in pruning of the skin and preventing dehydration
Dermis - Description
2 strata
serves as blood supply for epidermis
Dermis - Layers
Papillary stratum
Reticular stratum
Dermis - Papillary Stratum
Dermal papillae - aids in stability of holding dermis to underlying dermal layer
HAS: Meissner’s corpuscles, fibroblasts
Dermis - Reticular Stratum
serves as support and structure
lymphatic vessels - Langerhan’s can bring antigens here
dense irregular connective tissue (mostly collagen)
HAS: hair follicles and sebaceous glands
Meissner’s corpuscles
tactile sensory receptors for low frequency vibration and refined touch
Fibroblasts
assist with wound healing
Epidermal skin appendages
Hair and sebaceous and sweat glands
Derived from down growth of epidermal epithelium during development
Epithelium of these appendages can serve as a source of stem cells for skin wound repair
Secrete sebum to prevent water loss
Hypodermis/Subcutaneous Layer
Deepest layer of skin
Loose CT - adipose tissue (for insulation, body temp)
Sweat Glands –eccrine and apocrine
indicated by a lot of white space
HAS: Pacinian/Lamellar corpuscles
Pacinian/Lamellar corpuscles
mechanoreceptors for vibration and deep pressure
Integument Nerve Supply - Epidermal
Free nerve endings
Merkel’s cells
Integument Nerve Supply - Dermal
Ruffini’s corpuscles
Meissner’s corpuscles
Integument Nerve Supply - Hypodermal
Pacinian corpuscles
Ruffini’s corpuscles
mechanoreceptors for perception of heat, stretching, and sustained pressure on skin
