Cells and Tissues Flashcards
What is the overall function of the epithelium?
The function of the epithelium is for protection, absorption, secretion filtration and sensory sensation.
List the special characteristics of epithelium and relate these to function?
- Special contacts = consists of tightly packed cells that form a continuous sheet, via tight junctions or desmosomes.
- Polarity = all cells have an APICAL and BASAL side. Apical is exposed, free side, can have modifications such as microvilli. Basal is attached to the connective tissue layer.
- Basement membrane = epidermis is situated above a basement membrane called connective tissues, anchors the epidermis and prevents excessive stretch or tear. This layer is called the reticula lamina, a material secreted by both the epithelial cells and the connective tissue.
- Avascular = epidermis has no blood vessels and depends on the diffusion of substances from the vessels found in the underlying connective tissue. It is innervated by nerve fibers
- Regeneration = epithelial cells have a high regenerative ability, as long as they have a good supply of nutrients.
Describe the classification of ‘covering/ lining’ epithelium?
Two names are used for classification:
1) Number of layers
2) Shape of the cells
1) Simple = one layer, Stratified = multiple layers of cells
2) Squamous = flat, Cuboidal = cube-shaped, Columnar = tall and column-shaped.
State the defining histological features of each class of epithelium and relate these features to function?
SIMPLE:
1) Simple squamous- single layer of flattened cells with disc shaped central nuclei and sparse
cytoplasm- function in passage of materials by diffusion and filtration in sites where protection is
not important, also secretes lubricating substances in serosae.
2) Simple cuboidal- single layer of cube-like cells with large, spherical nucleus- function in
secretion and absorption.
3) Simple columnar- single layer f tall cells with oval nuclei, some cells bear cilia, may contain
goblet mucus secreting cells- function in absorption, secretion of mucus, enzymes and other
substances.
4) Pseudostratified columnar- single layer of cells of differing heights, some not reaching the free
surface, nuclei seen at different levels, may contain goblet cells and bear cilia- function in secretion
of mucus and propulsion of mucus by ciliary action.
STRATIFIED:
5) Stratified squamous- thick membrane composed of several cell layers, basal cells are cuboidal
or columnar and metabolically active, surface cells are flattened. Function in protecting underlying
tissues in areas subjected to abrasion.
6) Stratified columnar- several cell layers, basal cells usually cuboidal, superficial cells elongated
and columnar. (No stratified cuboidal)
7) Transitional- resembles both stratified squamous and stratified cuboidal, basal cells are cuboidal
and columnar, surface cells are dome shaped or squamous like. Functions in stretching readily and
permits distension of urinary organ by contained urine.
List the differences in structure and function between ‘covering/ lining’ epithelium and
‘glandular epithelium’
Structure of glandular- Unicellular glands are scattered within epithelial sheets. Multicellular glands
form invagination or evagination from an epithelial sheet, most have ducts connections to the
epithelial sheets.
Glandular epithelium functions in production and secretion of products or
substances
Covering epithelium functions to absorb, secrete, filtrate and sense.
Classify the endocrine and exocrine glands in terms of structure and function, and give
examples for each class?
- Endocrine = Ductless glands that produce hormones and secrete them directly into the blood.
Compact multi-cellular organs. e.g. - thyroid, adrenal gland, pituitary. - Exocrine = Have many epithelial lined ducts from which they produce and secrete their products,
secrete their products onto the body surface or into body cavities. E.g. exocrine pancreas
What are the components of connective tissue and give the function of each component?
1) Ground substance- unstructured material that fills space between the cells and contains the
fibres. Serves as a CT glue that allows cells to attach themselves to matrix elements. Functions as a
molecular sieve, or medium through which nutrients and other dissolved substances can diffuse
between capillaries and cells.
2) Fibres- provide support, collagen provides high tensile strength to the matrix, elastin helps in
stretch and recoil, reticulars support soft tissue of organs.
3) Cells- fundamental cell type exists in immature (blast) and mature (cyte) forms. Undifferentiated
cells secrete ground substance and fibres. Primary blast cells= fibroblasts in CT, chondroblasts in
cartilage, osteoblasts in bone and HSC in blood. Once blasts synthesize ground product matrix, the
mature. Mature cells maintain health of the matrix.
Classify the basic types of connective tissue according to their components, giving an example
of each type?
1) Mesenchyme (embryonic CT)- star shaped mesenchyme cells and fluid ground substance
containing fine fibrils. Fxn= differentiate into other CT’s or remain and provide source of new cells
in mature CT. E.g. mucous CT (supports umbilical cord)
2) CT PROPER:
LOOSE CONNECTIVE TISSUE:
a)Areolar - mast cells, macrophages, fibroblasts- function = wraps and cushions organs,
macrophages phagocytose bacteria, role in inflammation, hold tissue fluid.
b)Adipose - adipocytes, fate cells - function = provides reserve fuel, insulates against heat loss,
support and protect organs.
c) Reticular - reticular cells - function = form soft internal skeleton- stroma that supports other cell
types
DENSE CONNECTIVE TISSUE:
a)Dense irregular - collagen fibres, elastic fibres, fibroblasts – function = withstand tension,
provide structural strength.
b)Dense regular - collagen fibres, fibroblasts - function = attaches muscles to muscles or to bones ,
attach bone to bone, withstand tensile stress when pulling fore applied.
All mature CT belongs in proper CT except bone, cartilage and blood.
List the specialized forms of connective tissue (bone and CARTILAGE) and describe the histological
classification of each (CARTILAGE)?
Cartilage = avascular and lacks nerve fibers. Main cell types are chondroblasts that produce the matrix until the skeleton stops growing. Chondrocytes sit in the lacunae.
Type of cartilage:
a) Hyaline = most abundant, made of lots of collagen fibers. Chondroblasts produce glassy matrix and chondrocytes sit in the lacunae.
b) Elastic = similar to hyaline but has more elastin fiber allowing it to bend and stretch more.
c) Fibrocartilage = Intermediate between hyaline and dense connective tissue (e.g. ligaments), similar to hyaline but has less firm and more collagen. Found where hyaline meets ligaments or tendons. Compressive and resists tension well.
List the specialized forms of connective tissue (BONE and cartilage) and describe the histological
classification of each (BONE)?
Bone = is made of osseous tissue and is highly vascularized. Osteoblasts produce a much harder and tougher matrix and calcium or bone salts are produced and deposited in between fibers. Osteocytes sit in the lacunae Provide support and protection (e.g. skull).
List the histological feature of muscle tissue?
- highly cellular
- well-vascularized
- muscle cells have myofilaments (elaborate versions of myosin and actin)
Describe the histological feature of the 3 muscle types?
skeletal = long cylindrical cells. Multi-cellular cells and obvious striations
cardiac = branching cells with striations. Uni-cellular cells. Branching cells fit together well and meet special junctions called intercalated disks.
smooth = spindle-shaped cells. Central nucleus. Cells arranged to form sheets.
