Chapter 1: Epithelium Flashcards
What are the 3 general functions of Epithelium
- Absorption
- Secretion
- Provide a barrier
What are the 3 specialized functions of Epithelium
- Transport molecules across Epithelium
- Prevent transport of materials across Epithelium (selective permeability)
- Sensory (taste buds, retina in eye…)
What are some basic characteristics many types of Epithelium share
Cells are adjacent to each other (helps them provide a barrier)
Associated with a complete or partial basement membrane.
Epithelium is avascular (cells obtain nutrition by diffusion)
Associated with vascular connective tissue)
Cells are help together by cell junctions)
What are the 2 parts of a complete basement membrane
Basal lamina (produced by the Epithelial cells) Reticular lamina (produced by fibroblasts in connective tissue that is going to be near by)
What is the 1 part of a partial basement membrane
Basal lamina (produced by the Epithelial cells)
What are the 3 functions of a basement membrane
- Provides a surface for Epithelial cell attachment
- Molecular filter => limited
- Limited stretch => protective funtion
What are the 2 functions of Connective Tissue (CT)
- Provides nutrition
2. Source of defensive cells
What are the 4 types of Cell junctions (these are important)
- Zonula Occuldens (tight junctions)
- Zonula Adherens (adhesion junctions)
- Macula Adherens
- Gap Junctions
What are the functions of Zonula Occuldens
These junctions involve the sharing of intrinsic membrane proteins BETWEEN adjacent cells.
- Provides strong attachment
- Prevents the passage of materials between cells
What are the regions and functions of Zonula Adherens
Regions:
1. Cadherins (linkage proteins) between cells
2. Marginal bands (microfilaments) which attach the cytoskeleton to the cell membrane at these areas
Functions:
1. Strong attachment
2. Provide cell structural stability
What are the functions of Macula Adherens (desomosomes)
Provides strong attachment
What is a gap junction and its functions
Six connexins (proteins) arranged in a cylinder. The size of the openings can be controlled by the cells. A connexon= 1 complete structure.
Functions:
1. Strong attachments
2. Communication and exchange of materials
What is a Junctional Complex and what does it consist of
3 junctions in the following order beginning with the free cell surface:
- Zonula Occuldens
- Zonula Adherens (adhesion belt)
- Macula Adherens
What is the purpose of Hemidesmosomes
Help to connect Epithelial cells to the basal lamina (basement membrane)
What are Focal Point Contacts
Integrin (a transmembrane proteins of the cell membrane) binds to structural CT glycoproteins and also connect to cytoskeleton
What is Bullous Phephigoid
An autoimmune skin disease causing large blistering lesion that burst, but do heal
What is Pemphigus Vulgaris
An autoimmune skin disease causing skin blistering that do not heal easily, excessive bleeding likely and can be fatal
What are the 5 types of Simple Epithelium (epithelium that is a single cell thick)
- Simple Squamous
- Simple Cuboidal
- Simple Columnar
- Ciliated Pseudostratified Columnar Epithelium
- Surface Specializations
What are the details and functions of Simple Squamous cells
Cells should look flat (ex. lung, serosa on the outside of organs) A single later of flattened cells Functions: 1. Provide a barrier 2. Living filter
What are the details and functions of Simple Cuboidal Epithelium
A single layer of cube shaped cells (ex. exocrine ducts, thyroid follicular cells, kidney tubules) Functions: 1. Provides a barrier 2. Secretion 3. Absorption
What are the details and functions of Simple Columnar Epithelium
A single later of cells that have height, more cell cytoplasm than cuboidal, rectangular looking (ex. stomach, small intestines, gallbladder) Functions: 1. Provide barrier 2. Secretion 3. Absorption
What are the details and functions of Ciliated Pseudostratified Columnar Epithelium (respiratory epithelium)
This epithelium have 3 cell types of various heights so it can have the appearance of a stratified epithelium (ex. trachea, respiratory region of nasal cavity, bronchi) 3 cell types: 1. Goblet Cells 2. Ciliated Columnar Cells 3. Basal cells
What is the details and functions of a Goblet cell found in a Ciliated Pseudostratified cell
Modified columnar cell
Function:
To produce mucus
What is the details and functions of a Ciliated Columnar cell found in a Ciliated Pseudostratified cell
Columnar cells that contain CILIA (cilia are anchored in the apex of the cell by basal bodies)
Function:
To move mucus over the surface
What is the details and functions of a Basal cell found in a Ciliated Pseudostratified cell
Short pyramidal shaped cell that does not reach the surface
Function:
To be the stem cell for this type of Epithelium
What are the 4 different Surface Specializations types
- Microvilli
- Stereocilia
- Cilia
- Glycocalyx
What is a microvilli and its functions
Finger-like projections at the apical surface on some epithelial cells (also called brush boarder on a striated boarder)
Functions:
To increase surface area so as to increase absorption (ex. kidney tubule cells, small intestines)
What is a Stereocilia and its functions
Extremely long microvilli, usually fewer present than in microvilli (not related to true cilia)
Function:
Usually to increase surface area (ex. epididymis, cochlear hair cells)
What is a Cilia and its functions
Thin apical hair-like extensions of the cytoskeleton
Function:
To move something over a surface
What are two important points about cells with Cilia
- Cells have many mitochondria
2. Basal bodies block the free surface so there is NO secretion or absorption (ex. trachea, fallopian tube)
What is a Glycocalyx and its functions
Surface layer of glycoproteins and carbohydrates that covers some epitheliums (produced by epithelial cells) Functions: 1. Protections 2. Cell Recognition (ex. stomach and small intestines)
What is the definition of Stratified Epithelium and its 5 types
Definition: Epithelium that is 2 or more cell layers thick 2 Types: 1. Stratified Squamous 2. Keratinized Stratified Squamous= epidermis 3. Stratified Cuboidal 4. Stratified Columnar 5. Transitional (urinary)
What is the details and function of Stratified Squamous cells in Stratified Epithelium
Multiple layers of cells that tend to flatten out from basal later to superficial layer, superficial layer of cells are flat and alive (ex. esophagus, oral cavity, tongue, vagina)
Function:
Protection from abrasion
Problems and limitations:
1. Protection from drying
2.Limited thickness so protections is limited
What is the details and function of Keratinized Stratified Squamous in Stratified Epithelium
Multiple layers of cells that also ten to flatten from basal later to superficial layers of cells (superficial cells layer is covered by an added nonliving layer of keratin)
Functions:
Protection in a dry environment
What are the 5 layers in epithelium of the skin (important)
- Stratum Basale (germinativum)
- Stratum Spinosum
- Stratum Granulosum
- Straum Lucidum
- Stratum Corneum
What is Stratum Basale (germinativum)
1-2 layers of keratinocytes which are mitotic and closest to the dermis, “stem cells of the skin”
What is Stratum Spinosum
Multiple laters of :spiny shaped” keratinocytes produce lipids and keratohyline vacuoles. Keratinocytes have cytokeratin tonofilaments that radiate outward from the nuclear region. Thickness of this layer can vary.
What is Stratum Granulosum
Uppermost 2-5 layers of flattened living keratinocytes that contain flattened, condensed keratohyaline granules. Exocytosis of lipid–filled lamellar granules will occur from these cells.
What is Stratum Lucidum
Tthin layer of recently dead or dying keratinocytes present only in thick skin. This layer is not easy to see. Nucleus & organelles are not present.
What is Stratum Corneum
Layer of dead cells, keratin and lipids. Thickness of this layer varies but has three functions:
- Prevents water loss
- Provides a barrier
- Protects against abrasion or friction
What are Epidermal Pegs and Dermal Papillae
they contribute strength to the epithelium by increasing surface area for attachment of the epithelium to the CT below
How long do Keratinized Stratified Squamous cells live for
Cells have about a 28 day life cycle
What is a Melanocyte and where is it found
What: Cell that protects against US radiation
Where: Found in Stratum Basale. Numbers increase when exposed to UV light repeatedly
What is skin color greatly influenced by
- Enviromental Influence: increased US light exposure
- Genetics (Eurmelanin= more blackish color, Phenomelanin= more reddish tint)
- Number of blood vessels in dermis
What is a Langerhans Cell
Recognize external foreign antibodies.
Layers found in: Epithelial dendritic cell in Stratum Spinosum. Decrease with repeated UV exposure
What is a Merkel Cell
Provides tough receptor.
Layer found in: Stratum basale (associated with free nerve endings)
What is the details and function of a Stratified Cuboidal in Stratified Epithelium
Two layers of cells, basal layer typically flattened, superficial layer of cells is cuboid in shape, NOT COMMON (ex. large ducts in sweat glands and salivary glands).
Function:
To increase protection
What is the details and function of a Stratified Columnar in Stratified Epithelium
Two layers of cells, basal layer is flattened to cuboid in shape, superficial layer is columnar in shape, VERY RARE (large duct of pancreas, parts of male urethra, conjunctiva of the eye)
Functions:
1. To increase protection
2. To provide a transition between epithelial types.
What is the details and function of a Transitional (urinary) in Stratified Epithelium
Multiple layers of cells. Functions: 1. Protection 2. To stretch Specializations: 1. Thin, fenestrated basement membrane 2. Large, rounded superficial cells 3. Well developed Zonula occludens
What is Psoriasis Vulgaris
Patchy skin lesions. Accelerated keratinocyte life cycle (divides in about 1 week). Cells accumulate in stratum corneum. Inflammation in dermal papillae. Cyclic and etiology is unknown.
What are Freckles
Spots with extra pigment (especially in the fair skinned). An increase in melanin without an increase in melanocyte number. Tend to fade in winter and darken with sun exposure.
What is Vitiligo
Patches which lack melanocytes. Unknown cause but often associated with systemic diseases (hypothyroidism, hyperthyroidism, diabetes, Addison’s disease)
What are moles (naevi)
Discoloration due to a proliferation of melanocytes
What is Malignant Melanoma
Melanocytes become mitotically active and invade dermis. Very invasive and metastatic. Treatment: surgery and chemotherapy.
What is Albinism
Cause: melanocytes fail to produce melanin. Most common form: Tyrosinase (enzyme) is missing from melanocytes. It is a catalyst in the conversion of tyrosine to melanin.
What is the function of the exocrine system
Method of secretion by which the product is released into a duct or directly onto an epithelial surface
What is Parenchyma
Component directly involved with the primary function (ex. biceps= skeletal muscle)
What is Stroma
Components providing mechanical/metabolic support (ex. biceps= tendons, connective tissue, blood vessels, nerves)
3 Sub-classifications of exocrine system
- Morphology
- Method of secretion
- Product secreted
What does the sub-classification of Morphology contain
This method classifies the gland according to the shape of the secretory units (tubular vs alveolar) and the ducts arrangements (unbranched vs branched)
What does the sub-classification of Method of secretion contain (3)
- Merocrine (most common method of secretion, secretion by exocytosis therefore no cell damage)
- Holocrine (cell matures and dies, associated with odor, secretory product= entire cell with intact vacuoles)
- Apocrine (cell damage is minimal and cell not killed, associated with odor)
What does the sub-classification of Product Secreted contain
Acinus- smallest division of a gland (a group of cells surrounding a cavity).
Serous Demilune = A small group of serous cells attached to a mucus acinus
Myoepithelial Cells = contractile cells with epithelial origin. Cells wrap around the acinus and sometimes the duct in some exocrine glands.
What does Serous Glands produce and what are its characteristics
Produces: proteins.
Characteristics: Cell is trapezoid shaped, nucleus is typically round and noticeable, cells pick up stain
What does Mucus Glands produce and what are its characteristics
Produces: mucus.
Characteristics: Cells typically stain light, nucleus is often flat and peripheral
What does Mixed Glands produce and what are its characteristics
Produces: Serous and mucus.
Characteristics: Serous demilunes are possible
What is Endocrine Secretion
Secretory product released into nearby CT for vascular dispersal to target cell
2 Subtypes of Endocrine secretion
Paracrine: Signaling cell is close to target cell so the hormone does not enter the blood.
Autocrine: Signaling cell is its own target
2 Regulation of Endocrine Secretion
- Hormonal: + and - feedback loops
2. ANS= autonomic nervous system
