Histology Pt.1

Slide preparation

  1. Fixing Tissues

1cm cubes

  1. Embedding tissues

Dehydrate (alcohol) and embedd in wax

  1. Sectioning Specimum

3-10 microns thick

  1. [frozen sectioning]

Alternative for fresh samples, rapid turnover

  1. Basic Staining Technique

a. Remove wax using a solvent

b. Staing with Haemotoxylin (H) = nuclei purple

c. Differentiate with acid-alcohol + basic (Scott's tap) water rinse

d. Satin w/ Eosin (E) = cytoplasam red, then mount

Alternative Staining technique

Periodic-acid Schiff (PAS)

detectspolysacchrides, glycogen, mucin

Masson's trichorme

Muscles, RBC (red), Collagen (blue), Cytoplasam (pink) nuclei (black)

Epithelium

Connective Tissue

Epithelial tissues are sheets of specialized cells that adapt to cover and line the exterior and interior surfaces of the body

Derivative

Ectoderm

Mesoderm

Endoderm

Form the epidermis, fingernails and toenails, hair

Sweat and sebaceous glands, salivary glands and the mucous glands of the mouth and nose

Tooth enamel

Form the inner lining of blood vessels and lymphatic vessels.

Digestive and respiratory tract (except the mouth and nasal cavity) and the glands secreting into the digestive tract,

Form

Arranged in cohesive sheets with little extracellular matrix

Attached to the connective tissue via the basement membrane

Nutrients/Waste products is perfomed via diffusion

Type

Simple squamous, cuboidal or columnar (1 cell)

Stratified squamous, cuboidal, pesudostratified columnar (>1 cell)

Ex. Squamous = endothelium in blood or lymphatic vessels

Ex. Cuboidal = small salivary ducts (secretion/adorption)

Ex. Columnar = GI tract (mucos secretion/adorsption)

Ex. Pseudocolumnar = nasal cavity (often ciliated)

Ex. Statified squamous = keratinised or non-keratinised seen in the gingiva or mucosa of cheek

Basement Membrane

Features include rete ridges/pegs = connective tissue papillae

A permeable barrier of extracellular matric proteins and GAGs (glycosaminoglycans)

Adheres the epithelium to the underlying connective tissue

A resivour for growth factors - for tissue development, repair and support

Layers

Basal lamina

GAGs and laminin = Barrier to transport

Reticular lamina

Type IV collagen = provides strength

Substrata

Lamina lucida

Lamina densa

associated with hemidemosomes - by way of a collagen fiber network

Epithelial Cell junctions

Occluding(Tight) junctions

Anchoring Junctions

Communicating Junctions

Ring adhesion protien - links with neighbouring cells to form a tight barrier

Prevents the diffusion of substances between cells at the cells apex

Often seen in epithelium of oral mucosa nd slaivary/ mucous glands

adherent junctions

actin fibers are linked via cadherins proteins - they incircle adjacnet cuboidal/columar cells together

basal to tight junctions

focal contact area

regulate cell architecture and transmit mechnaical forces between adjacent cells

Intergrins anchor cells to the extra cellular matix

prodvide adhesion and intermechanical signalling

desmosome

Intacellular plaques form strong adherent bonds by linking intermediate filaments of neihbouring cells together

desmoglein and desmocollin = cadherins

hemidesmosome

half a desmosome - anchors the epitjhelial cell to the ECM

protrudes from the cell in to the lamina lucida

Gap junctions

Made up of several hundred pores. A pore is a six-protein subunit (connexon) of which half is found in each cell

Direct cell-cell signallng (K+, Ca++, cAMP, gluscose ect)

Quick turnover, allowing for fast adaptation

Derivative

Mesoderm

Ectomesenchyme

A scattered network of cells producing a extracellualr netowrk of fibrillar proteins in a ground substance

Ground Substance

A viscous GAG gel containing fibrous lamin and fibronectin as well as water

GAGs (glycosaminoglycans) - inflexibale polysacchrides that provide stiffness and viscosity to the matix = low compressibility

GAGs are hydrophillic and trap water = 10% of GS is GAGs and the remainder is water

Ex. hyularonic acid

Water is important for exchnage of nutrients and metabolic wastes beteen cells/blood supply

Matrix is secreted by fibroblasts (in cartilage and bone it is chondro/osteoblasts)

Fibers

Collagens

Elastin

Fibrillin

Fibronectin

Major Types (I, II, III, IV)

Type I = resist tensile forces

Type II = (cartilage) compressibilty/shock adsorption

Type III = reticular fibers found in the Basement membrane for attachement

Type IV = sheetlike found in BM, external laminae, lens capsules

Forms elastic fibers which are covalently linked

A glycoprotein that forms fibrils to organise the elastin fibers into elastic fibers

Circulates in tissue plasma and is important in tissue repair

Cells

Fibroblasts

Osetoblasts

Chrondoblasts

Myofibroblasts

The primary connective tissue cell

Flat-ovoid shpe = secrete/maintain the ECM

Nb: appearance depends of activity (inactive cells often refered to as fibrocytes)

Exihibit smooth muscle contractility (ie lots of actin filamanets)

Build the ECM of cartilage

Build the ECM of bone

Undifferentiate mesenchymal cell

Pluripotent cells able to differnetiate into any c.t. cell

Example

Dense C.T.

Cells = fibroblasts

ECM = Collagen fibers heavily packed in teh ECM, parallel (regular) or random (irregular)

Cartilage

Cells = Chrondrocytes

ECM = Ex. Collagen II (hyaline cartilage), elastic fibers (elastic cartilage), collegen I (fibrocartilage)