Chapter 1 Flashcards
4 basic types of tissue
epithelial
connective
nervous
muscle
General functions of Epithelium
Absorption
Secretion
Provide a barrier
Specialized functions of epithelium
transport of molecules across epithelium
prevent transport of materials (selective permeability)
Sensory (taste buds, retina)
Basic Characteristics of Epithelium
- Cells are adjacent to each other
- Associated with complete or partial basement membrane
- Avascular, obtains nutrition by diffusion
- Associated with vascular connective tissue
- Cells held together by cell junctions
Compele basement membrane components
Basal lamina (from epithelium) Reticular lamina (from fibroblasts in CT)
Partial basement membrane components
basal lamina only
Functions of basement membrane
- provides surface for epithelial cell attachment
- molecular filter- very limited
- limits stretch
- directs migration of cells (healing)
Functions of vascular connective tissue
- provides nutrition
2. source of defensive cells
Types of cell junctions
Zonula Occludens
Zonula Adherens
Macula Adherens
Gap Junctions
Zonula Occludens
aka Tight Junction
involves the sharing of intrinsic membrane proteins (interacting proteins) between adjacent cells
Function of Zonula Occludens
- Provides strong attachment
2. Prevents the passage of materials between cells
Zonula Adherens
aka Adhesion belt
Consists of:
1. cadherins (linkage proteins between cells)
2. marginal bands (microfilaments) that attach cytoskeleton to cell membrane
Functions of Zonula Adherens
- strong attachment
2. Provides cell structural stability
Macula Adherens
contains:
transmembrane proteins
protein plaque
Tonofilaments
Macula Adherens function
provides strong attachment
Gap junctions
6 connexins arranged in a cylinder
size of the openings controlled by the cell
Connexon = 1 complete structure
Gap Junction function
strong attachment
transport materials between cells
Junctional Complex
free edge
Zonula occuldens
Zonula adherens
Macula Adherens
Hemidesmosomes
help connect epithelial cells to basal lamina
Focal Point Contacts
Integrin (transmembrane protein) binds to structural CT glycoproteins and connects to cytoskeleton
Bullous Pemphigoid
Autoimmune skin disease that causes large blisters that burst but Heal
Cause: antibodies bind to proteins in hemidesmosomes
Pemphigus Vulgaris
Autoimmune skin disease causes blisters that Don’t Heal. Can be fatal
Cause: antibodies bind to parts of desmosomes
Cholera
Acute bacterial infection of small intestines
Cause: toxins disrupt proteins in zonula occludens, permiting the loss of water and electrolytes from CT below epithelium
Types of Simple Epithelium
Simple Squamous
Simple Cuboidal
Simple Columnar
Ciliated Pseudostratified Columnar Epithelium (respiratory epithelium)
Simple Squamous
single layer flattened cells
ex. Lungs, parietal layer Bowman’s capsule, serosa on outside of organs
Functions of Simple Squamous
living filter
Provides a barrier
Secretion
Simple Cuboidal
Single layer of cube shaped cells whose nucleus occupies much of the cytoplasm
ex. Exocrine ducts, thyroid follicular cells, kidney tubules
Functions of Simple Cuboidal
Absorption
Secretion
Provides a barrier
Simple Columnar
Single layer of cells that have height and more cytoplasm that simple cuboidal
ex. stomach, small intestines, gallbladder, larger exocrine ducts
Ciliated Pseudostratified Columnar (Respiratory Epithelium)
Contains 3 cell types of various heights
Ex. trachea, respiratory region of nasal cavity, bronchi
Cell Types in Respiratory Epithelium
Goblet Cells
Ciliated Columnar Cells
Basal Cells
Goblet cells
modified columnar cell
Functions to produce mucus
Ciliated Columnar Cells
contain cilia that are anchored to apex of cell by basal bodies
Functions to move mucus over surface
Basal Cells
short pyramidal cells that do not reach the surface
Functions as the stem cell for this type of epithelium
Types of Surface Specializations
Microvili
Stereocilia
Cilia
Glycocalyx
Microvili
Aka: brush border of striated border
Finger like projections at the apical surface o some epithelial cells
ex. kindney tubule cells, small intestines
Microvili function
to increase surface area so as to increase absorption
Stereocilia
very long and more rare type of microvili. Not related to true cilia- non-motile w/ rigid actin core
ex. epididymis, cochlear hair cells
Stereocilia Function
to increase surface area
Cilia
thin apical hair-like extensions of the cytoskeleton
- cells have many mitochondria
- basal bodies block the free surface, so there is no absorption or secretion
ex. trachea, oviduct
Cilia Function
to move something over a surface
Glycocalyx
surface layer of glycoproteins and carbohydrates that covers some epithelium
- produced by epithelial cells
Ex. stomach and small intestine
Glycocalyx Function
Protection, cell recognition
Stratified Epithelium and types
2 or more cell layers thick, named for shape of superficial cells. All have protective function
Stratified Squamous Keratinized Stratified Squamous Stratified Cuboidal Stratified Columnar Transitional (Urinary)
Stratified Squamous
multiple layers of cells that flatten superficially. Superficial layer of cells are flat and alive
Ex. Esophagus, oral cavity, tongue, vagina
Function of Stratified Squamous
protection from abrasion in moist environment
Limitations of Stratified Squamous
No protection from drying
Limited thickness bc superficial cells are alive and recieve nutrition by diffusion, so protection is limited
Keratinized Stratified Squamous
multiple layers of cells that tend to flatten superficially.
Superficial layer covered by an added nonliving layer of keratin
Ex. Skin
Function of Keratinized Stratified Squamous
protection in a dry environment
Layers in epithelium of skin
stratum basale (germinativum) Stratum spinosum Stratum granulosum Stratum lucidum Stratum Corneum
Stratum basale (germinativum)
1-2 layers of keratinocytes that are mitotic and closest to the dermis
Stratum Spinosum
- multiple layers of “spiny shaped” keratinocytes that produce lipids and keratohyaline vacuoles
- Keratinocytes have cytokeratin tonofilaments that radiate out from the nuclear region
- Thickness varies
Stratum Granulosum
- uppermost 2-5 layers of flattened living karatinocytes that contain flattened, condensed keratohyaline granules
- exocytosis of lipid-filled lamellar granules occurs here
stratum lucidum
- thin layer of recently dead or dying keratinocytes present only in thick skin
- not easy to see, nucleus and organelles not present
Stratum corneum
- layer of dead cells, keratin and lips. Variable thickness
-3 functions:
prevents water loss
Provides a barrier to microbes
protects against abrasion
Keratinocytes
- typical cell type
- can divide in stratum basale
- produces keratins/keratohyaline granules and lipids in stratum granulosum
- 28 day life span
Structures that contribute strength to keratinized stratified squamous
Epidermal pegs (rete ridges) and dermal papillae. increase surface area for attachment of epithelium to CT below
Other cell types in Keratinized stratified squamous
Melanocytes
Langerhans cells
Merkel cells (epithelial tactile cells)
How Melanocytes function
- Keratinocytes phagocytize the cytoplasmic tips of the melanocytes contraining the melanosomes with the melanin
Function of Melanocytes
- protect against UV radiation
- about equal # in all humans
Layer location of Melanocytes
Stratum basale
Influencers of Skin color
- Environmental influences (UV light increases melanocyte #s and melanin
- Genetics
- # of blood vessels in dermis
How Genetic influences skin color
Eumelanin (dark) or pheomelanin (red)
placement of melanin
Destruction of melanin by lysosomes
Langerhans cells
Aka epidermal dendritic cell
- recognize and process external antigens
- Antigen presenting cells
Layer location of Langerhans cells
Stratum Spinosum
Merkel Cells
aka Epithelial tactile cells
- provide touch receptors
- associated with free nerve endings
Merkel cell layer location
Stratum basale
changes in melanocyte and Langerhans cell levels in response to UV light
Melanocyte levels increase
Langerhans cells decrease
Stratified Cuboidal
2 layers of cell. Flattened basal layer and cuboid superficial layer (not common)
ex. larger ducts in sweat glands and salivary glands
Stratified Cuboidal Functions
increase protection
Provide a barrier
Stratified Columnar
2 layers of cells. Flattened to cuboid basal layer. Columnar superficial layer (very rare)
ex. large ducts in pancreas, parts of male urethra, conjunctiva of eye
Function of Stratified Columnar
- to increase protection
- provide transition between epithelial types
- Provide a barrier
