4 - skin histology Flashcards
What are the 4 main tissue types talked about in histology?
- Epithelial tissue
Connective tissue
Muscle tissue
Nervous tissue
Name the 6 steps to prepare tissue for histology
- Take sample
- Fixation
- Selection and trimming
- Processing and embedding
- Sectioning
- Staining
How do you take a sample for histology?
Take a sample at biopsy or post mortem
Use a needle to remove it to avoid squishing it
Describe fixation step in histology
You fix the tissue in fixative like formalin.
This hardens and preserves tissue (stops them rotting and makes them easier to cut) but you get some tissue shrinkage
Describe the selection and trimming step in histology prep
Trim the bit your interested in
Describe the processing and embedding stage in histology prep
The specimen is put through a machine that processes it and embeds it into a material like paraffin wax - so the cells are dehydrated and replaced with wax, it gives a block around the tissue and makes the tissue a similar hardness so it can be cut
Describe the sectioning step of histology prep
Take thin slices of the tissue
What is the standard histo stain?
H and E
Name the components of H and E stain and describe them and what they stain
Haematoxylin = purple/blue, its a basic dye. It binds to acids like nucleic acids so stains nuclei blue
Eosin = pink/red. Its an acidic dye. It binds to bases like proteins
What does Massons trichrome stain?
Collagen - blue
What does Verhoeff–van Gieson stain?
Elastic fibres - black
How do immunohistochemical stains work?
They use antibodies to bind to a tissue specific antigen and a second flourescently labelled antibody to bind to the first antibodu
What tissues does the ectoderm form?
Epidermis and adnexa
What tissues does the mesoderm form?
Dermis, subcutis and blood vessles
What tissues does the endoderm form?
Respiratory tract, GIT, liver and pancreas
What tissues does the neuroectoderm form?
Neurones and melanocytes (from neural crest cells)
What are the 8 functions of skin?
- Protection
- Sensory
- Secretory
- Heat regulation
- Excretory
- Osmoregulation
- Vitamin D synthesis
- Display
What are the 6 things that make up the dermis?
Collagen and elastic fibres Fibroblasts Immune cells (mast cells) Adipocytes Nerves and blood vessels Adnexa
What are the 2 layers of the dermis?
Papillary dermis (top layer) and reticular dermis.
Name the 5 types of epithelium
- Simple squamous
- Simple cuboidal
- Simple columnar
- Stratified squamous
- Transitional
What type of epithelium is the epidermis?
Why?
Stratified squamous keratinising epithelium
Because it is made up of many layers = stratified
The more superficial cells are thin and flat = squamous
The surface layer is keratin = keratinising
What amino acid is melanin derived from?
Tyrosine
What are nociceptors?
Pain receptors
What do nociceptors respond to?
To tissue damage caused by chemical, mechanical or thermal stimulation
Name the 2 types of sweat glands and give both names for them
Eccrine AKA atrichial
Apocrine AKA epitrichial
How is sweat secreted?
From contraction of specialised myoepithelial cells which surround the glands
What is sebum composed of?
A mix of lipid and dead sebaceous cells
Name 4 glands that are derived from sebaceous glands
Meibomian glands (eyelids), heptoid (perianal) glands, uropygial (preen) glands and some specialised scent glands.
Name the 3 types of hair follicle
Simple hair follicle
Compound hair follicle
Sinus hairs
Which species have simple hair follciles?
Horses, cattle, pig and humans
Which species have compound hair follciles?
Dog, cat, sheep and goats
