ToB Flashcards
Define histology
Study of the structure of tissues by means of special staining techniques combined with light and electron microscopy
Define tissue
Collection of cells specialised to perform a particular function
Aggregations of tissues constitute organs
Value of histology
Biopsy and histology is the final proof of most diseases
For diagnoses purposes
E.g. Lung and breast cancer
Angstrom in meters
10^-10 m
Size of most cells
10-20micrometers
Define biopsy
Removal of a small piece of tissue from an organ or part of the body for microscopic examination
Define smear test
Collect cells by spontaneous/mechanical exfoliation
What is a smear test used for?
Cervix and buccal cavity
Define curettage
Remove tissue by scooping and scraping
Define needle
Put needle into tissue to gather cells
Define direct incision
Cut directly into tissue of interest and remove tissue
Define endoscopic
Removal of tissue via instruments through an endoscope
Uses of curettage
Endometrial lining of uterus
Uses of needle biopsy
Brain Breast Liver Kidney Muscle
Uses of direct incision
Skin
Mouth
Larynx
Uses of endoscopy
Lung
Bladder
Intestine
Uses of trans vascular biopsy
Heart
Liver
Fresh biopsy examples
Needle biopsy
Wet and bloody
Define fixed biopsy
Macromolecules cross-linked
Cellular structure preserved
No autokysis or putrefaction
Commonly used fixatives
Glutaraldehyde
Formaldehyde
What causes shrinkage artefacts
Tissue is dehydrated and rehydrated in
Slide preparation process
What is a shrinkage artefact?
Abnormalities in final slide
What does haematoxylin stain?
Acidic components of cells
Nucleolus (RNA)
Chromatin (DNA)
Purple/Blue
What does eosin stain?
Basic components of cells
Most cytoplasmic proteins
Extracellular fibres
Pink
What does Periodic Acid-Schiff stain?
Carbohydrates
Glycoproteins
Magenta
What is phase contrast?
Uses interference effects of two combining light waves
Advantages of phase contrast
Enhancing the image of unstained cells
Define dark field
Exclude unscattered beam (light/electron) from the image
Advantages of dark field
Live an unstained sample
Define fluorescence
Target molecule of interest with fluorescent Ab
Define confocal
Tissue labelled with one or more fluorescent probes
Advantaged of fluorescence
Uses multiple fluorescent stains on one specimen
Advantages of confocal
Eliminates ‘out of focus flare’
3D from a series of 2D images
Imaging of living specimens
Define epithelia
Sheets of contiguous cells of varied embryonic origin that cover external surface of the body and line internal surfaces
Embryonic origin of epidermis and corneal epithelium
Ectoderm
Embryonic origin of epithelium of urogenital tract Blood and lymphatic vessel lining Pericardial and pleural sac lining Peritoneal lining
Mesoderm
Embryonic origin of
Epithelia of resp and GI tract, of liver and many glands
Endoderm
Define simple
One cell layer thick
Define endothelium
Lining of blood vessels
Define mesothelium
Lining of body cavities
Pericardium, pleura, peritoneum
Epithelia of blood vessels
Simple squamous
Epithelia of mesothelium
Simple squamous
Basement membrane position
Thin, flexible, acellular layer which lies between epithelial cells and subtending connective tissue
Basement membrane structure
Basal lamina laid down by epithelial cells, lies closest to them
Thickness can inc by variably thick layer of reticular fibrils (type3collagen) elaborated by the subtending connective tissue
Basement membrane function
Strong flexible layer to which epithelial cells adhere
Cellular and molecular filter
Degree of penetration of basement membrane by malignant cells highly relevant to prognosis
Where are micro villi occludin?
Simple columnar epithelia
What does microvilli occludin do?
Binds adjacent plasma membranes tightly together in apical portions of some epithelia
Form zona occludens
Membrane proteins cannot pass
Renewal rate for epithelia
Describe
Constant rate for each epithelia
Differs depending on location and fUnction
When is turnover rate of epithelia not constant?
Injury leads to acceleration
Turnover rate of skin
28 days
Turnover rate of small intestine epithelia
4-6 days
Are all epithelia renewed?
No
But proliferation can be triggered to replace damaged/lost cells
Define microvilli
Apical extensions that greatly increase the surface area for selective absorption of intestinal contents
Define stereocilia
Very long microvilli
Extend from the surface of the ductus deferens and the epididymis
May have absorptive function
Define cilia
Extensions form cells that beat in coordinated waves
9+2 configuration
Where are cilia found ?
In lining of trachea - sweep mucus n dirt out of lungs
In Fallopian tubes - move ovum from ovary to uterus
Classifying glands
Destination of secretion
Structure of gland
Nature of secretion
Method of discharge
Define exocrine
Gland with ducts
Define endocrine
Ductless gland that secretes directly into the blood
Simple multicellular glands
Ducts don’t branch
Complex/compound multicellular gland
Ducts branch
Define mucous gland
Secretions containing mucus rich mucins
highly glycosylated polypeptide
Such cells stain poorly in H&E sections
Define serous glands
Secretions often enzymes are watery and free of mucus
Eosinophilic pink H and E section
Methods of secretion
Merocrine
Apocrine
Holocrine
Describe Merocrine secretion
Membrane bound vesicle approaches cell-surface
Vesicle fuses with plasma membrane
Contents of vesicle are in continuity with the extracellular space
Plasma membrane is very slightly larger
Membrane retrieved stabilising cell-surface area
Examples of merocrine secretion locations
Salivary glands
Pancreas
Examples of apocrine secretion locations
Mammary glands
myoepithelial cells assist secretion
Describe Apocrine secretion
Non-membrane-bound structures e.g. Lipid approaches cell-surface
Make contact and pushes up apical membrane
Thin layer of apical cytoplasm drapes around droplet
Menbrane surrounding droplet pinches off from cell
Plasma membrane is very slightly smaller
Membrane added to regain original surface area
Location of Holocene secretion
Sebaceous gland
Describe Holocene secretion
Disintegration of the entire cell
Release of contents
Discharge of whole cell
Define endocytosis
Process of engulfing material initially outside the cell
Opposite to exocytosis (merocrine secretion)
What is coupled in trans epithelial transport?
Endocytosis and exocytosis
When is trans epithelial transport used?
When molecules are too large to penetrate membranes
Describe trans epithelial transport
Material endocytosis at one surface of the cell
Transport vesicle shuttles it across the cytoplasm
Material/vesicle then exocytosis at the opposite surface
Golgi apparatus structure
Stack of disc-shaped cisternae
One side of the disc flattened, other side concave
Discs have swelling at their edges (vesicles that bud off)
Distal swellings pinch off as migratory Golgi vacuoles
Golgi apparatus function
Sorting into different compartments
Packaging through condensation of contents
Adding sugars to proteins and lipids (glycosylation)
Transport
Golgi apparatus product destination
Majority extruded in secretory vesicles
Some retained for use in cells (e.g. Lysosomes)
Some enter the plasma membrane (Glycocalyx)
Golgi apparatus - glycosylation and specificity
Branching sugars offer complex shapes for specific interaction in the Glycocalyx
Enzymatic destruction of this layer alters specificity based properties of cells
Specificity based properties of cells determined by Glycocalyx
Adhesion to substrates and neighbouring cells
Communication with neighbouring cells
Contact inhibition of movement and division
Mobility of cells
What makes cells more specific?
Sugars
Simple mechanisms that control secretion
Nervous control
Endocrine control
Neuro-endocrine control
Negative feedback chemical mechanism
Example of nervous control of secretion
Sympathetic nervous stimulation of adrenal medullary cells
Leads to release of adrenaline
Example of endocrine control of secretion
Adrenocorticotrophic hormone ACTH stimulate the cortex of the adrenal gland to secrete hormones
E.g. Cortisol
Example of neuro-endocrine control of secretion
Nervous cells of the hypothalamus control ACTH secretion from the anterior pituitary gland
Example of negative feedback chemical mechanism of secretion
Inhibitory effect of high thyroxine (T3&T4) levels on TSH synthesis by the anterior pituitary gland
Recognising exocrine gland
Unicellular glands (goblet cells) in jejunum and colon
Parotid glands
Submandibular glands
Recognise endocrine glands
Pancreas
Thyroid gland
Parathyroid gland
Adrenal (suprarenal) glands
Secretion by parotid glands
Exocrine
Secretion by submandibular glands
Exocrine
Secretion by pancreas
Endocrine
Secretion by thyroid glands
Endocrine
Secretion by parathyroid glands
Endocrine
Secretion by adrenal (suprarenal) glands
Endocrine
What do mucous membranes line?
Internal tubes that open to the exterior
Alimentary tract
Respiratory tract
Urinary tract
Mucous membranes consist of:
Epithelium (type depending on site) lining the lumen of a tube
Adjacent layer of connective tissue often referred to as the lamina propria
In the alimentary tract, 3rd layer consisting of smooth muscle= muscular is mucosae
Muscularis mucosae
What is the smooth muscle in alimentary tract also known as?
What is the adjacent layer if connective tissue in mucous membrane also known as?
Lamina propria
What are serous membranes?
Thin, two part membrane that line certain closed body cavities (spaces which do not open to the exterior)
What do serous membranes envelop?
The viscera
Examples of serous membranes
Peritoneum
Pleural sacs
Pericardial sac
What does the pericardial sac envelop?
The heart
What does the peritoneum envelop?
Many abdominal organs
What do the pleural sacs envelop?
The lungs
What do the serous membranes secrete?
Lubricating fluid
Promotes relatively friction free movement of structures they surround
Serous membrane consists of:
Simple squamous epithelium (mesothelium)- secretes watery lubricating fluid
Thin layer of connective tissue - attaches to epithelium to adjacent tissues (also carries blood vessels and nerves)
Define the term limit of resolution
Minimum distance that two objects can be distinguished at
Limit of resolution is proportional to
Wavelength
Theoretical limit of resolution for light microscope
0.2 micrometers
Theoretical limit of resolution for an electron microscope
0.002nm
Structure of bilipid membrane
Phospholipid bilayer (membrane) forms a relatively impermeable barrier to most water-soluble molecules Phospholipid molecules which make up cell membrane are amphipathic
Function of bilipid membrane
Protein molecules dissolved in the lipid bilayer mediate most of the other functions of the membrane
Structure of Glycocalyx
Cell ‘coat’ made up of oligosaccharide and polysaccharide side chain on the outside of the plasma membrane
Function of Glycocalyx
Side chains are a way of giving the cell specificity
Functions of plasma membrane
Selective permeability Transport of materials along the cell surface Exocytosis Endocytosis Intercellular recognition Signal transduction Intercellular adhesion
Functions of nucleus
Stores cell’s DNA
Coordinates cell’s activities
metabolism, growth, protein synthesis, mitosis
Structure of nuclear envelope
Double layered membrane that separates the contents of the nucleus from the cellular cytoplasm
Has lots of nuclear pores
Function of nuclear envelope
Nuclear pores allow specific types and sizes of molecules to pass back and forth between the nuclear and cytoplasm
Attached to a network of tubules called the endoplasmic reticulum
Describe nucleolus
Inside nucleus
Synthesises protein-producing macromolecular structures called ribosomes
Describe ribosome
Site of translation
Used for protein synthesis
Structure of rough endoplasmic reticulum with ribosomes
Membrane of RER continuous with outer layer of nuclear envelope
Ribosome only binds when it begins to synthesise a protein destined for the secretory pathway
Functions of RER
Lysosomal enzymes with mannose-6-phosphate marker added in cis-Golgi network
Secreted proteins constitutively or regulated
Initial glycosylation N-linked (O- linked in Golgi)
Where is smooth ER found
Liver and mammary gland (lipid synthesis)
Ovaries, testis, adrenal glands (steroidogenesis)
Golgi apparatus structure
Saucer shaped stacks of cisternae
Vesicle transport in Golgi
Vesicles bud off from the RER and fuse with the convex cis face of the Golgi body
Golgi bodies have polarity such that proteins migrate from the convex to the concave trans face of the stack
Functions of the Golgi apparatus
Modify, sort, concentrate and package proteins synthesised on the RER
Vesicles leaving Golgi
Destined for lysosomes assembly or
Secretion - secretory vesicles are condensed to granules then contents released at cell surface by exocytosis
