What is meant by the term tissue?
A collection of cells specialised to perform a particular function
Why is histology valuable to diagnosing disease?
The study of tissues can reveal and be final proof of a range of diseases
Eg cancer
What is a smear and what tissues can it be used to sample?
Collection of cells via spontaneous/mechanical exfoliation, then smeared on slide
Cervix or buccal cavity
What is Curettage and what tissues can it be used to sample?
Removal of tissue via scooping or scraping
Endometrium of uterus
What is Needle biopsy and what is it used to sample?
Needle used to gather cells
Brain, kidney, muscle, breast, liver
What is direct incision biopsy and what tissues is it used to sample?
Cut into and remove tissue
Skin, larynx, mouth
What is Endoscopic biopsy and what tissues can it be used to sample?
Removal via endoscope instrument
Lung, intestine, bladder
What tissues can trans vascular biopsy be used to sample?
Heart, liver
Why does biopsied tissue require fixation?
Preserves cellular structure by cross linking macromolecules
No autolysis or putrefaction
Commonly used fixatives for tissue include?
Glutaraldehyde, formaldehyde
Why do shrinkage artefacts arise in preserved tissues?
Dehydration and rehydration during fixing
Why is histological staining useful?
Different types of tissue can be stained different colours/shades to allow differentiation between them
Haemotoxylin staining is taken up by _________
Acidic components of cells eg Nucleolus or chromatin
What colour is conferred onto tissue that take up haemotoxylin?
Purple/blue
Eosin staining is taken up by ________
More basic components of cells eg most cytoplasmic proteins and extra cellular fibres
Eosin staining confers what colour?
Pink
Periodic acid schiff (PAS) stains what cellular components what colour?
Carbohydrates, glycoproteins
Magenta
What is Phase contrast microscopy and what advantages does it have?
Uses interference of two combined light waves
Enhances un-stained cell image
What is dark field microscopy and what advantages does it have?
Uses light not directly aimed at objective lens
Enhances contrast in un-stained samples
What is confocal microscopy and what advantages does it have?
Tissue labelled with fluorescent probes
Can be used to generate a 3D image from a series of 2D images
Define epithelia
Sheet of contiguous cells of varying embryonic origins that cover external and internal surface of the body
What external or internal opening to external space does epithelia cover?
Skin
Alimentary tract
Respiratory tract
Genitourinary tract
What interior spaces that don’t open to exterior are covered by epithelium?
Pericardial sac Pleural sac Peritoneum Blood vessels Lymphatic vessels
Where can simple squamous epithelium be found?
Lining the blood vessels (endothelium) Lining of body cavities (mesothelium) Alveoli Inner and middle ear Bowman's capsule and Loop of Henle in the kidney
Functions of simple squamous epithelia include?
Relate this to location
Lubrication (visceral linings)
Gas exchange (alveoli)
Barrier (Bowman’s capsule)
Active transport via pinocytosis (meso/endothelium)
Where are simple cuboidal epithelia found?
Thyroid follicles
Ducts of exocrine glands
Kidney tubules
Surface of ovary (germinal epithelium)
Function of simple cuboidal epithelia include?
Relate this to location
Absorption and conduit (exocrine glands)
Absorption and secretion (kidney tubules)
Barrier (ovary)
Hormone synthesis, storage and mobilisation
Simple columnar epithelium are found where?
Stomach lining Small intestine and colon Gallbladder Large ducts of exocrine glands Uterus Oviducts Ductili efferents of testis
Functions of simple columnar epithelia include?
Relate this to location
Absorption (intestines and gallbladder)
Secretion (stomach lining, gastric pits, intestines)
Lubrication (small intestine and colon)
Transport (oviducts)
Pseudo stratified epithelia is found where?
Lining of nasal cavity, bronchi and trachea
Epididymis and ductus deferens
Auditory cavity and part of tympanic cavity
Lacrimal sacs
Large excretory ducts
Functions of pseudo stratified epithelia include?
Relate this to location
Secretion and conduit (upper resp tract and ductus deferens)
Absorption (epididymis)
Mucus secretion (URT)
Particle trapping and removal (URT)
Stratified squamous non keratinised epithelia can be found where?
Oral cavity Oesophageal Larynx Vagina Part of anal canal Surface of cornea Inner surface of eyelid
Functions of stratified squamous non keratinised epithelia include?
Relate this to location
Protection against abrasion (all sites)
Reduces water loss while remaining moist.
Stratified squamous keratinised epithelia can be found where?
Surface of skin
Limited distribution in oral cavity
Functions of stratified squamous keratinised epithelia include?
Relate this to location
Protection from abrasion and trauma Prevents water loss Prevents ingress of microbes Shields from UV damage (All sites)
Stratified transitional epithelia (urothelium) found where?
Renal calices
Ureters
Bladder
Urethra
Functions of stratified transitional epithelia include?Relate this to location
Distension
Protection from toxic chemicals
(All sites)
Where would you find a basement membrane?
Between epithelia and subtending tissues
Describe a basement membrane
Consists of basal lamina
Thickness variable with introduction of type III collagen
Thin, flexible and acellular
Function of basement membrane?
Epithelium adheres to it
Cellular and molecular filter (prevents malignant ingress through it)
Epithelial cell renewal rate can be described as?
Constant rate for different epithelia
Rate of renewal for skin epithelium?
28 days
Rate of renewal for small intestine epithelia?
4-6 days
Epithelia renewal can be triggered by?
Damage or trauma
Epithelial regeneration rate depends on?
Location and function
What are microvilli and what is their function?
Apical extensions to increase surface area of intestinal epithelium
Increase surface area for selective absorption
What are stereo cilia and what is their function??
Very long microvilli found in Ductus deferens and epididymis
May have absorptive function
What are cilia and where are they found? What do they do?
Apical cell extensions on respiratory epithelia and in oviducts
Beat in waves
Sweep mucus and dirt out of respiratory tract
Move the ovum down the oviduct
Feature the 9+2 micro tubule configuration.
What is the purpose of microvilli occludin in simple columnar epithelia?
Creates the zona occludens
Binds the cells together tightly in apical portion of cells, restricts proteins to either basal or apical surfaces