Intro to Histology (9/4b) Flashcards by Victoria Brady

4 Basic Tissue Types

Epithelial
Connective
Nervous
Muscle

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Epithelial Tissue - Description

Superficially lines almost everywhere in the body

Avascular

Cell-cell junctions

Functional polarity

Basement membrane

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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)

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3 main functions of cell-cell junctions

Barrier
Structural
Communication

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3 main types of cell-cell junctions

Occluding/Tight junctions
Adhering/Anchoring junctions
Communicating/Gap junctions

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Occluding/Tight junction

some things can get through but nothing can get between the functions

(EX: blood brain barrier)

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Communicating/Gap junction

connection of proteins that forms a channel, relays a message to the next cell as it gets stretched or compressed

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3 Types of Adhering junctions

Desmosomes
Hemidesmosomes
Zonula adherens

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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

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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

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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

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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

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Functional polarity

has apical and basal surfaces that have polarity

Apical = faces lumen/external surface

Basal = faces ECM

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Apical layer types

Simple
Pseudostratified
Stratified

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Simple cell layer

Thickness: 1 layer

Shapes: simple-squamous, cuboidal, columnar

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Pseudostratified cell layer

Thickness: 1 layer, all cells touch basal lamina but not all reach apical surface

Shapes: pseudostratified columnar

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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

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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