IMMS Histology Flashcards
Composition of cartilage?
Cells:
- Chondroblasts
- Chondrocytes
Matrix:
* Hydrophilic chondroitin sulphate-rich amorphous jelly, compressible - made up of glycoaminoglycans (GAGS)
Types of Cartilage?
Hyaline-
* Joins- glassy amorphous matrix
Elastic (similar structure to hyaline and fibrous)-
* Pinna of ear and epiglottis - visible elastic fibres within matrix. Able to spring back to its original shape more easily than other types of cartilage
Fibrous-
* Intervertebral discs - visible collagen fibres within the matrix. Collagen fibres are arranged in order, parallel to each other > gives extra strength
Composition of bone?
Cells:
- Osteoblasts: actively synthesise bone
- Osteocytes: maintain bone & regulate calcium levels
- Osteoclasts: break down bone and aid in remodelling bone [from a different stem cell to that of osteoblasts & osteocytes]
Matrix:
- Organic: mostly collagen (type 1)
- Inorganic: calcium mostly in the form of crystalline hydroxyapatite
Types of bone:
Primary bone or woven bone: first to be formed, disorganised (random) matrix
Secondary bone or lamellar bone: remodelled bone, laminated- lighter and stronger
What does primary and secondary bone mean?
Primary bone: firs to be formed, even after a fracture
Secondary bone: remodelled bone, highly organised, lighter and stronger
How do you describe the gross appearance of bone?
- Spongy: has holes (bone marrow found here), lightweight, centre of long bones
- Cancellous: holes, see also spongy
- Compact: usually secondary bone, outer shafts on long bones
How to describe the mode of formation of bone?
- Membrane: formed directly in a mesenchyme, primary bone
* Endochondral: formed by replacement of cartilage
How to describe deposition of bone?
- Osteons: Haversian systems, secondary bone, concentrically deposited around
central vessels - Appositional: Deposited in layers on external surface of bones
Role of bacteria?
Epithelia form barriers: for protection (skin), for absorption (gut) and for secretion
(pancreas)
What are the two main types of epithelium (a layer/layers of cells that rest on a basement
membrane that line a cavity)?
Simple: Single layer of cells (lungs)
Stratified: Many layers of cells (skin)
Pseudostratified epithelia don’t fit into either category
Types of simple epithelium?
SIMPLE SQUAMOUS
EPITHELIUM:
single layer of flattened cells with parallel oval nucleus. They have a very thin cytoplasm, giving a large plate like cell, with a bulge where the nucleus is - plate like/fried egg in shape - found in the alveoli of the lungs
SIMPLE CUBOIDAL EPITHELIUM:
Single layer of cells, roughly square in profile, with a round nucleus. Found in the collecting ducts of kidneys and ducts of glands.
SIMPLE COLUMNAR
EPITHELIUM:
Single layer of cells taller than wide with an oval, perpendicular nucleus. Is the epithelium that lines the inside of the intestines, gall bladder and some airways (bronchus). Microvilli or cilia may be present.
What is microvilli?
Regular finger-like projections from the apical surface of absorptive cells
What is cilia?
Regular motile appendages on the apical surface of cells of parts of the respiratory and female reproductive tracts
What is the feature of protective function of stratified epithelia?
Protective function, composed of many layers of cells, continually being worn down, worn- away cells are replaced from below due to the presence of stem cells
Found in areas where there is continuous abrasion
Subtypes of stratified epithelia?
Squamous (plates): keratinised - skin, non keratinised - mouth, oesophagus & vagina - WATERPROOF
Cuboidal (squares): found in some large ducts - NOT WATERPROOF
Types of stratified epithelium
Stratified squamous non-keratinised epithelium:
found in the mouth, oropharynx, oesophagus & vagina. Basement membrane lies between epithelium & supportive connective tissue.
Stratified squamous keratinised epithelium:
found on outside of body as hairy or non- hairy skin. Cells on surface of skin are dead, have no nuclei and are full of keratin
Pseudo-stratified epithelia: Stretchable, cells piled up on a basement membrane. Looks like layers of cells when there is actually only one layer
Epithelial junctions
Adherent (tight) junctions:
band-like fusions between cells that are impervious to most molecules
Desmosomes: plaques that form physical joint between cells and connect the cytoskeletons of adjacent cells
Gap junctions: electrical
junctions that permit the transfer of small molecules
Basement membrane?
VITAL COMPONENT OF ALL EPITHELIA
Composed of several extra-cellular proteins including Collage IV and fibronectin
Separates the epithelium from underlying connective tissue
Essential for the proper functioning and survival of epithelium - without a basement
membrane the epithelial cells tend to die, in cancer the cancerous epithelial cells break through the basement membrane to spread [EPITHELIAL STRUCTURES ARE MOST LIKELY TO DEVELOP CANCER]
Types of muscle?
Visceral (smooth) muscle/ involuntary muscle: found in arterial wall, wall of
intestine, airways of lungs, bladder and ureters. Fusiform cells with an oval nucleus
Voluntary (skeletal) muscle: found in skeletal muscles, larynx, diaphragm & eye
Cardiac muscle: found in heart, base of great vessels (aortic or pulmonary artery)
Origins of connective tissue?
Mainly derived from undifferentiated mesenchymal cells; fibroblast, fat cells & most cartilage and bone cells.
But also from the haemotopoetic stem cell line: monocytes, macrophages, lymphocytes, mast cells, blood cells & others
Types of connective tissue?
Fibrous: loose or dense (tendon)
Hard: cartilage or bone
Fatty: white (adults) & brown (babies)
Types of collagen?
Many different types, often tissue specific
Tropocollagen: composed of a triple helix of peptides
Fibroblasts: secrete tropocollagen units
Fibres: assembled extra-cellularly
More than 12 different types: • Type I: skin, tendon, organs and bone • Type II: cartilage • Type III: liver • Type IV: basement membranes • Type V: placenta
Types of fatty tissue?
White fat:
Large cells with single fat globule in
each cell. Usually appears empty (white) in slides since fat is extracted during processing
Brown fat:
Cells with many globules of fat. Found across shoulders and down back of newborn - important in neonatal-thermoregulation since they generate heat on breakdown
