Unit 7: Histology (tissues) Flashcards
(25 cards)
What is histology?
- The study of tissues
- Tissue:
- a group of cells w/ sim.
structure and function - cells of most tissues are
surrounded by an extracellular
fluid called interstitial fluid
(mostly water and ions)
- a group of cells w/ sim.
- 4 major tissue types (everything in body will fall under one of these, but there are subtypes)
- Epithelial Tissue (have these
on the outside and the inside -
on any internal or external
holes/cavities) - Connective Tissue
- Muscle Tissue
- Nervous Tissue
- Epithelial Tissue (have these
What are cell junctions? (in some tissues) - what are the 3?
- points of contact btw. adjacent
cells - seen in epithelial tissue,
some nervous and muscle cells - ALL formed by cell membrane
proteins - 1 = tight junctions, 2 = anchoring junctions, 3 = gap junctions
What are tight junctions?
- are a partial fusion of specific proteins on the lateral surface
- form ring-like tight seal
- prevents material from passing between cells (like bacteria, proteins, sometimes fluid or ions - depending on the tissue)
- stops integral proteins from moving btw. apical (lumen exposed surface) and basolateral (attached) surfaces of the cell
What are anchoring junctions? (e.g. desmosomes)
- proteins that fasten cells to each other and/or extracellular material (“rivets” cells together)
What are gap junctions?
- open channels (formed by proteins) through the adjacent cell membranes interconnecting the cytosols of the cells
- allows ions/small molecules to pass from one cell to another
- tissues can then work as a unit:
- imp. in cardiac and smooth
muscle (allows synchronization
of contractions) - also found in epithelial tissue
- imp. in cardiac and smooth
What is epithelial tissue?
- covers body surface and line body/organ cavities
- organ cavity = lumen (but can be filled with anything - like air or liquid like blood etc.)
What are the 3 main characteristics of epithelia?
- has 1 free surface (either on
outside of body or inside) - little extracellular space btw.
cells - all avascular = no blood vessels
- basement membrane
- extracellular layer
- attaches epithelium to
underlying connective tissue
layer (formed by epithelial and
connective tissues) and acts like
“Velcro”)
What are the classifications of epithelia?
- most subtypes are classified and named according to:
- the number of cell layers
sitting on the basement
membrane
a) one layer = simple
b) more than 1 layers =
stratified - shape of the cells in the apical
layers (= layer touching the
free surface)
c) flattened = squamous
b) round or cube shaped =
cuboidal
e) rectangular = columnar
- the number of cell layers
What are the types of epithelial tissue?
- simple epithelia = 1 layer
- allows exchanges of molecules
(gasses, nutrients, ions) -
absorption/secretion
a) simple squamous = 1 layer of column shaped (tall and thin) cells (like lungs)
b) simple cuboidal = 1 layer of
cube shaped cells (like
kidneys)
c) simple columnar = 1 layer of column shaped (tall & thin) cells (like stomach and small intestine
- allows exchanges of molecules
What are (2) stratified epithelia (> areas of abrasion?)
- protective (areas of abrasion)
- predominant subtype is stratified squamous = apical cells squished (flat)
- like epidermis of skin
What are (3) pseudostratified epithelia?
- “falsely” stratified
- columnar cells that appear stratified (some cells are shorter and nuclei appear at diff. levels, but ALL cells sit on basement membrane (= simple)
- e.g. lines most of respiratory tract (where cells are also ciliated = ciliated pseudostratified epithelium)
What are (4) transition epithelia?
- = cell shape (and layering) varies w/ structuring
- only in inner lining of urinary system
- cuboidal to squamous when stretched
What are (5) glandular epithelium?
- are for secretion
- so if epithelial cells form a gland, the cell layer(s)/cell shape classification is no longer used and tissue is called glandular epithelium
What are the subtypes of glandular epithelium?
a) Exocrine glands
a. Secrete products onto body surface or into a body
cavity, and can be:
i. Unicellular (like goblet cells, secrete mucus [into a
cavity], and in digestive, urinary, reproductive, and
respiratory tracts)
ii. Multicellular – consists of secretory and duct cells
(ducts connect secretions to surface or cavity
1. E.g. glands: sudoriferous (sweat), sebaceous (oil),
mammary, digestive
b. Endocrine glands
i. No ducts (ductless)
ii. Secrete hormones into the extracellular fluid
(interstitial fluid) surrounding glandular cells that
then enter the blood plasma for transport and
target cells/tissues
iii. E.g., thyroid gland secretes thyroid hormones
What are the functions of Epithelial tissues?
- Protection (often stratified or squamous) - like epidermis of skin
- Secretion - glandular epithelium - like thyroid bland, sweat glands
- Allows selective passage of materials (nutrients, waste, water, ions) across membranes - typically simple epithelia - like kidney, intestine, capillaries
What is connective tissue (CT)?
- mainly supports and connects tissues
- cells far apart, separate by extracellular matrix that usually forms the bulk of the tissue
- extracellular material give connective tissue subtypes
their identifying characteristics
- extracellular material give connective tissue subtypes
- variable vascularity
What are the CT cell types?
Cell names ending in:
- BLAST - create matrix (like osteoblast, chondroblast, fibroblast)
- CYTE - maintain matrix (like osteocyte, chondrocyte, fibrocyte)
- CLAST - break down matrix)
What are the matrix compositions of CT?
- Fibres (proteins)
- collagen fibres (for strength)
- elastic fibres (contain elastin - allow strength and recoil)
- reticular fibres (form networks - like CT part of basement
membrane)
- Ground Substance
- water (interstitial fluid - ISF) and large organic molecules
(proteins and carbs) surrounding cells and fibres
- water (interstitial fluid - ISF) and large organic molecules
What are the classifications of CT? (mainly by matrix composition)
- Connective Tissue Proper
- Cartilage
- Bone
- Blood = fluid CT
Info on Connective Tissue Proper
Cells = fibroblasts/fibrocytes except adipose tissue (adipocytes)
Types:
a) Loose CT:
i. areolar connective tissue (ex. = lamina propria)
- loosely arranged collagen and elastin fibres
- highly vascular
ii. adipose connective tissue
- very little matrix
- cells large (adipocytes), store triglycerides - tissue looks
like “chicken-wire”)
- highly vascular
b) Dense CT:
- many fibres (therefore dense CT is aka fibrous CT)
- little ground subtypes; poorly vascular
- two types:
i. dense regular CT
- collagen fibres running in the same direction
- ex. = tendons and aponeuroses - connect muscle to
bone
- ex. = ligaments - connect bone to bone
Info on Cartilage (it’s very smooth looking)
- cells = chondrocytes (located in cavities in the matrix called lacunae) and chondroblasts
- large amounts of matrix:
a) fibres = collagen & elastin (proteins)
b) ground substance is mostly water, but is firm due to the
type of organic molecules present - avascular - heals slowly
- 3 types:
a) hyaline cartilage - most abundant
b) elastic cartilage - many elastic fibres (like epiglottis and
ear pinna)
c) fibrocartilage - high in collagen fibres
- “shock absorbers” - like intervertebral discs, pubic
symphysis
Info on bone
- cells = osteocytes (in lacunae), osteoblasts, and osteoclasts
- large amounts of matrix:
a) fibres = abundant collagen
b) ground substance
- inorganic calcium (Ca++) phosphate salts and organic
components (proteins and carb.s) that make it rigid
- very vascular
Info on blood (fluid CT)
- cells: red blood cells (RBC) and white blood cells (WBC), platelets
- extracellular matrix is called plasma
a) contains soluble fibres (e.g. fibrinogen for blood clotting)
b) ground substance is mostly water w/ ions, proteins
What is muscle tissue?
- contractile
- subtypes:
- skeletal (striated)
- cardiac (striated)
- smooth (non-striated)
