Histology Flashcards
What do epithelia form barriers for?
Protection (skin)
Absorption (gut)
Secretion (pancreas)
What is simple epithelia?
A single layer of cells on a basement membrane
What is stratified epithelia?
-Two or more layers of cells on a basement membrane
-Continually worn down and replaced
-Protective function
-At sites of abrasion
Describe simple squamous epithelia
-Single layer of flattened cells on a basement membrane
-Parallel oval nuclei (1 per cell)
-Line inside of blood vessels, mesothelium and peritoneum
Describe simple cuboidal epithelia
-Single layer of cells with similar height/width on a basement membrane
-Central spherical nuclei
-Line kidney tubules and small ducts (sweat glands, salivary, pancreas)
Describe simple columnar epithelia
-Single layer of taller cells on a basement membrane
-Line stomach, intestine and uterus
-May or may not have cilia/microvilli
What are microvilli?
-Tiny projections on luminal surface of absorptive cells
-Increase surface area
-Intestinal brush border
-Need an electron microscope to see
What are cilia?
-Microscopic motile projections on luminal surface
-In respiratory and reproductive tract
Where are stratified squamous epithelia?
Non-keratinising: mouth, oesphagus, vagina, oropharynx
Keratinising: waterproof layer in skin
What’s psuedostratified epithelia?
-Single layer of cells of varying heights, mimicking multiple layers
-All cells in contact with basement membrane
-Line conducting airways
Describe urothelium
-Surface layer of umbrella cells
-Pseudostratified between umbrella cells
-Lines collecting part of urinary tract
What are epithelial junctions?
-Occluding junctions prevent diffusion between cells
-Desmosomes joins cytoskeletons of adjacent cells
-Gap junctions allow transfer of small molecules and ions between adjacent ep cells
What can undifferentiated mesenchymal cells give rise to?
- mast cell
- fibroblast
- chondroblast
- osteoblast
- adipocyte
Three divisions of connective tissue
Fibrous: loose/dense
Hard: cartilage/bone
Fatty: white/brown
What are the 5 different types of collagen?
1: skin
2: cartilage
3: (reticulin), in liver, bone marrow and spleen
4: basement membranes of epithelia
5: placenta
Characteristics of collagen
- Extracellular fibres stain pink with H+E
- variable thickness and lengths
- often run in bundles
Characteristics of loose connective tissue
- widely spaced thin collagen fibres
- fibroblasts/cytes
- unstained ground substance
Characteristics of dense connective tissue
- closely spaced thick collagen fibres
- fibroblasts/cytes
- unstained ground substance
- irregular or regular
Characteristics of reticulin
- type 3 collagen
- scaffold to bone marrow, liver, kidney, lymph node and spleen
- not visible on H+E, need a silver stain
Characteristics of elastin
- produced by fibroblasts
- fine fibres or sheets of elastin
- stains pink on H+E
- may be branched
Characteristics of white adipose tissue
large cells with single fat globule
usually appear empty as fat extracted
Use of H+E + colours
H stains nuclei and RNA blue
E stains colloidal proteins, most components of cell cytoplasm, and keratin pink/red
Use of Van Gieson stain and colours
Collagen pink/red
elastic van gieson stain elastic fibres brown/black
Muscle stained yellow
Use of Alcian Blue and colours
GAG, mucous goblet cells, mast cell granules and cartilage matrix all blue