Histology Flashcards
What is pseudostratified columnar epithelia?
Single layer of cells of differing heights
What is transitional epithelia?
Where the basal cells are cuboidal or columnar and the apical cells are squamous or dome-like
What is mesothelium?
Simple squamous epithelia which lines closed body cavities
What are exocrine glands?
Ducted glands which secrete substances onto epithelium
What are endocrine glands?
Duct-less glands which secrete substances directly into the blood
What is a serosa?
Complex tissue which lines closed body cavities and consists of epithelia and underlying connective tissue
How many microns are there in a millimeter?
1,000
What are all connective tissue cells derived from?
Mesenchymal cell
Name the 5 types of connective tissue
Fibrocollagenous, cartilage, blood, bone, fat (adipose)
How is fibrocollagenous tissue classified?
By quantity of collagen fibres, type of collagen fibre, and organisation of collagen fibres
Describe loose/areolar fibrocollagenous connective tissue
Relatively little type I collagen (in random directions), some type III collagen, some elastic fibres, has fibroblasts, mast cells, macrophages and some white blood cells
Describe dense irregular fibrocollagenous connective tissue
Abundance of collagen type I (in random directions), some elastic fibres, fibroblast is main cell, provides ability to withstand tension in many directions
Describe dense regular fibrocollagenous connective tissue
Abundance of collagen type I (in one direction only), few elastic fibres, mainly fibroblasts, found in tendons and most ligaments, withstands great tensile strength if force applied in one direction
Describe reticular fibrocollagenous connective tissue
Fine meshwork of collagen type III, loose ground substance, soft internal skeleton formed by fibres (stroma), mainly found in lymphoid organs
Describe white adipose connective tissue
Main adult fat store, insulates, shock absorber, made of unilocular adipocytes (lipids fuses into one big droplet)
Describe brown adipose connective tissue
Involved in thermoregulation in neonates, multilocular adipocytes, organised into lobules by fibrocollagenous septa
Describe the extracellular matrix of cartilage
Sulphated GAGs, rich in proteoglycans and hyaluronic acid and type II colalgen
What are the different types of cartilage?
Hyaline, elastic and fibrocartilage
Where do chondrocytes lie?
In lacunae (lake)
Describe fibrocartilage and where it is found?
Contains both type I (stronger) and type II collagen fibres and is found in IV discs, pubic symphysis, and knee menisci
What is the perichondrium?
A specialised layer of condensed, highly vascular fibrocollagenous tissue with chondroblasts embedded (for repair)
What are muscle cells derived from?
Mesoderm
What is the basement membrane of muscle cells called?
External lamina
Why does muscle stain bright pink?
Due to large amounts of myofilament in cytoplasm
Describe endomysium
Supporting reticular fibre network which carries capillaries and nerves to the muscle cells (fibres)
Describe perimysium
Surrounds muscle fascicles
Describe epimysium
Surrounds whole muscle with collagen and elastic fibres embedded, it is continuous with tendons and muscle attachments
What are satellite cells?
Stem cells which can add to muscle, and are found beneath the basement membrane
What do fibroblasts do in muscle?
Help produce endomysium
What is the H-zone?
Just the myosin filament, no overlap with actin
What is the I-band?
Just the actin filament
What is the A-band?
All of the myosin filament, including overlap with actin
What is the M-line?
Thickest portion of the myosin filament
What is the Z-line?
Marks end of sarcomere (actin)
Describe cardiac muscle cells
Branching, multinucleate cells which meet at intercalated discs
Why does a fibrocollagenous scar form in cardiac damage?
Cardiac muscle doesn’t have any satellite cells and therefore cannot repair itself and a scar forms instead
Describe smooth muscle cells
Spindle-shaped cells with a central nuclei, no striations and that are closely arranged to form sheets
What are myoepithelial cells?
Cells which have processes which surround secretory portions of exocrine glands, and contraction allows movement into the duct
What are myofibroblasts?
Specialised cell that produces collagen it also have actin and desmin filaments which have a large role in wound healing –> proliferate to produce fibrocollagenous scar –> contraction reduces the size of damaged area in healing process
What are pericytes?
Stem cells that are associated with capillaries and venules, and following injury proliferate to form new endothelial cells, fibroblasts or myofibroblasts
What does a Nissl stain show?
It stains RNA and DNA
What is a nervous system nucleus (or PNS ganglion)?
Collection of neurones with common circuity and function (in grey matter)
What is neuropil?
Dense tangle of neuroal axons, dendrites and glial processes and is site of communication between various components
What glial cells are present in the central nervous system?
Oligodendrocytes, astrocytes and microglia
Describe astrocytes
Highly branched cell that surrounds the surfaces of neurones and blood vessels in the CNS and an important part of the BBB; proliferates at the site of injury to form a ‘glial scar’
Describe oligodendrocytes
Produce myelin by wrapping membrane around axons (one cell can myelinate many axons)
Describe microglia
Specialised macrophages in CNS (smallest cell and hard to see without stain)
What glial cells are present in the peripheral nervous system
Schwann cells and satellite cells
Describe Schwann cells
Myelinate axons (1 Schwann cell segment per axon)
Describe satellite cells
Similar to the astrocytes of the CNS (physical and metabolic support)
Define ‘motor unit’
Motor neurone and all of the skeletal muscle fibres it contracts
What does immunohistochemistry involve?
Using labelled antibodies to detect specific antigens in tissue secretions; primary antibody binds to antigen and then a secondary antibody binds to that antibody with a marker e.g. fluorescence
