ANA 203 Histology Epithelial tissue Flashcards
What is histology?
This is the study of the tissues of the body and how they are arranged to constitute organs
What are the 4 fundamental tissues?
Epithelial tissue
Connective tissue
Muscular tissue
Nervous tissue
What is the function of the extracellular matrix?
- Furnish mechanical support for the cell
- Transport of nutrients to the cell
- Transport of catabolites and secretory products
Cell theory
- Life exists only in cells
- The cell is the smallest unit of life
3.The continuity of life has a cellular basis
What are cell inclusions?
Accumulations of materials that are not metabolically active
What is necrosis?
Necrosis is the death of body tissue
What is apoptosis?
Apoptosis is the process of programmed cell death
Difference between a prokaryotic and eukaryotic cell
prokaryotic cells
1) no true nucleus
2) no internal membranes
3) single, circular chromosome
Eukaryotic cell
1) true nucleus
2) internal membranes and organelles
3) multiple chromosomes
Difference between a prokaryotic and eukaryotic cell
prokaryotic cells
1) no true nucleus
2) no internal membranes
3) single, circular chromosome
Eukaryotic cell
1) true nucleus
2) internal membranes and organelles
3) multiple chromosomes
Function of muscle and other contractile cells
movement
Which cells form adhesive and tight junctions between cells
Epithelial cells
Function of fibroblasts, cells of bone and cartilage
Synthesize and secrete components of the ECM (extra-cellular matrix)
Which specialized cells convert physical and chemical stimuli into action potentials?
Neurons and sensory cells
Function of the mucus gland cells
Synthesis and secretion of mucous substances
Function of the cells of the kidney and salivary gland ducts
Ion transport
Which cells are involved in intracellular digestion?
Macrophages and some white blood cells
Purpose of fat cells
Lipid storage
Functions of epithelium
1.Protection (skin),
2. Absorption (Small & large intestine),
3. Secretion (glands),
4. Excretion (tubules of the kidey),
5. Gas exchange (lung alveolus),
6. Gliding btw surface (mesothelium) and
7. Ion transport (GIT)
8. Contractility (e.g., myoepithelial cells).
General characteristics of epithelium
- They are derive from ectoderm, mesoderm and endoderm,
- They line and cover all body surfaces except the articular cartilage, the enamel of the tooth,
- they lines a body cavity,
- They are anchored by a basal lamina ( BL
+ CT = BM) - Forms most glands
Special characteristics of epithelium
- Cellularity
cells are in close contact with each other with little or no intercellular space between them - Specialized contacts
may have junctions for both attachment and communication - Polarity
epithelial tissues always have an apical and basal surface - Support by connective tissue
at the basal surface, both the epithelial tissue and the
connective tissue contribute to the basement membrane - Avascular
nutrients must diffuse - Innervated
- Regeneration
epithelial tissues have a high capacity for regeneration
What are the 3 domains of the epithelia line surfaces cavities
- the apical domain (AD), 2. lateral domain
AD
(LD), - basal domain (BD)
Function of the three domains of an epithelium
- The apical domain is exposed to the lumen or external environment.
2. The lateral domain faces neighboring epithelial cells linked to each other by cell adhesion molecules and junctional complexes.
3. The basal domain is associated with a basal lamina that separates the epithelium from underlying connective tissue.
What is the basement membrane?
The basal lamina–connective tissue complex
BL + CT = BM
The apical domain of some epithelial cells
can display three types of differentiation:
- Cilia
- Microvilli
- Stereocilia
What are the factors holding epithelial cells together?
Adhesion proteins link plasma membranes of adjacent cells
Contours of adjacent cell membranes
Special cell junctions
Types of cell junctions
Tight Junctions
Adherens/anchoring junctions
Gap junctions/communicating
Features of tight junctions
Tight junctions (zona occludens) – close off intercellular space
1. They define the polarity of the cell
2. Found at apical region of most epithelial types
3. Some proteins in plasma membrane of
adjacent cells are fused
4. Prevent molecules from passing between cells of epithelial tissue
5. Associated with actin filaments
Features of a gap junction in cells
Gap junctions – passageway between two adjacent cells
Let small molecules move directly between neighboring cells
Cells are connected by hollow cylinders of protein
Location of simple squamous epithelium
Renal corpuscles/bowmans capsule
Alveoli of lungs
Lining of heart, blood, and lymphatic vessels
Lining of ventral body cavity (serosae)
lining of the heart
Location of simple squamous mesothelium
Lines peritoneal, pleural and pericardial cavities
Location of simple squamous endothelium
Lining of blood vessels
Pleural cavity/pleura
Surrounding the lungs
Pericardial cavity/ pericardium
Surrounding the heart
Peritoneal/peritoneum
Surrounding the abdomen
What is the main function of the simple squamous cells
- secretes lubricating substance in serosae
- allows diffusion and filtration of materials
Location of simple cuboidal epithelium?
- secretory ducts of small glands
- proximal and distal convoluted kidney tubules
- thyroid gland/follicles
- surface covering of the ovary
Function of simple cuboidal epithelium
Secretion and absorption
What is epithelial tissue?
Is one of the four basic types of animal
tissue.
Refers to the layers of cells that line hollow
organs, flat surfaces, and glands.
It covers the whole surface of the body. It
is made up of cells closely packed and
arranged cells
What are 5 general characteristics of epithelial cells?
- They are derive from ectoderm,
mesoderm and endoderm, - They line and cover all body surfaces
except the articular cartilage, the enamel
of the tooth, - they lines a body cavity,
- They are anchored by a basal lamina ( BL
+ CT = BM) - Forms most glands
Special characteristics of Epithelial cells (7)
Special Characteristics
1. Cellularity: cells are in close contact with each other with little or no
intercellular space between them
2. Specialized contacts: may have junctions for both attachment and communication
3. Polarity: epithelial tissues always have an apical and basal surface
4. Support by connective tissue
at the basal surface, both the epithelial tissue and the connective tissue contribute to the basement membrane
5. Avascular: nutrients must diffuse
6. Innervated
7. Regeneration: epithelial tissues have a high capacity for regeneration
What forms the basement membrane?
the basal lamina-connective tissue complex
What are cell junctions?
Cell junctions are symmetrical
structures formed between two
adjacent cells.
Classification of cell junctions
Symmetrical
Asymmetrical
Types of symmetrical junctions
- Tight junctions (occluding junctions)
- Belt desmosome (zonula adherens or
adhesive or anchoring junctions): - Desmosomes (macula adherens or spot
junction). - Gap or communicating Junction
Types of asymmetrical junction
Hemidesmosomes
3 major classes of symmetrical junctions
- Tight junctions
- Anchoring junctions
- Gap or communicating junctions
Gap junctions are not anchoring
junctions but communicating junctions
linking adjacent cells TRUE/FALSE
TRUE
Where are anchoring junctions found?
Anchoring junctions are found below the
tight junctions, usually near the apical
surface of epithelium.
Classes of anchoring junctions
- The zonula adherens or belt
desmosome - The macula adherens or spot
desmosome - The hemidesmosome
Features of desmosomes
Desmosomes (macula adherens) – two disc-like plaques
connected across intercellular space
Plaques of adjoining cells are joined by
proteins called cadherins
Proteins interdigitate into extracellular space
Intermediate filaments insert into plaques
from cytoplasmic
What is the basal lamina?
- Noncellular supporting sheet between the epithelium and the connective tissue deep to it
- Consists of proteins secreted by the epithelial cells
Function of the basal lamina
- Acts as a selective filter, determining which molecules
from capillaries enter the epithelium - Acts as scaffolding along which regenerating epithelial
cells can migrate
What structure determines which molecules from the capillaries enter the epithelium
The basal lamina
Pseudostratified colmunar epithelia
Pseudostratified columnar epithelia
* appear to have multiple cell layers,
* but all cells are in contact with the basal lamina
Simple Squamous epithelium
Description
single layer of flat cells with disc-shaped
nuclei
Special types
Endothelium (inner covering)
slick lining of hollow organs
Mesothelium (middle covering)
Lines peritoneal, pleural, and pericardial cavities
Covers visceral organs of those cavities
Simple Cuboidal epithelium
Description
single layer of cube-like cells with large,
spherical central nuclei
Simple columnar epithelium
single layer of column-shaped (rectangular)
cells with oval nuclei
Some bear cilia at their apical surface
May contain goblet cells
Function of simple columnar epithelium
Function
Absorption; secretion of mucus, enzymes,
and other substances
Ciliated type propels mucus or reproductive
cells by ciliary action
Location of simple columnar
Non-ciliated form
Lines digestive tract,
gallbladder, ducts of
some glands
Ciliated form
Lines small bronchi,
uterine tubes, ute
Pseudostratified columnar
description
All cells originate at basement membrane
Only tall cells reach the apical surface
May contain goblet cells and bear cilia
Nuclei lie at varying heights within cells
Gives false impression of stratification
Function of Pseudostratified columnar
secretion of mucus; propulsion of mucus by cilia
Location of pseudostratified columnar epithelium
Sterociliated type
Ducts of male
reproductive tubes
Ducts of large glands
Ciliated variety
Lines trachea and most
of upper respiratory
tract
Stratified squamous epithelium
Many layers of cells – squamous in shape
Deeper layers of cells appear cuboidal or
columnar
Thickest epithelial tissue – adapted for
protection
What is the thickest epithelial tissue?
Stratified squamous epithelium
What are the types of stratified squamous epithelium?
Keratinized – contain the protective protein keratin
Surface cells are dead and full of keratin (dry areas)
Non-keratinized – forms moist lining
Function of stratified squamous epithelium
Protects underlying tissues in
areas subject to abrasion
location of stratified squamous epithelium
Keratinized – forms epidermis of skin
Non-keratinized – forms lining of
esophagus, mouth, eye, and vagina
Transitional epithelium
Basal cells usually
cuboidal or columnar
Superficial cells dome-shaped or squamous
Function of transitional epithelium
stretches and permits
distension of urinary
bladder
Location of transitional epithelium
Lines ureters, urinary
bladder and part of urethra
Which waterproof protein allows our skin to be waterproof?
Keratin
What type of epithelia is in the trachea and why?
Pseudostratified columnar ciliated epithelium because it creates mucus which traps air particles and cilia which aids propulsion of muscus
Function of anchoring junction Zonula Adherens
Transmembrane linker proteins attach to actin microfilaments of the cytoskeleton and bind adjacent cells
Along with tight junctions, form the tight
the junctional complex around the apical lateral
borders of epithelial tissue
Which cell junction is not a cell to cell junction?
Hemidesmosomes, it is a cell to ECM junction or cell to basal lamina junction
