Principles Histology Flashcards
Give four structures common to all eukaryotic cells:
- Outer membrane
- Inner cytosol
- Cytoskeleton
- Membrane bound organelles
(Other structures within the cell many or may not be bound by a membrane; these areas are called inclusions)
What is the plasmella and what does it do?
(cell membrane) It separates the cytoplasm from the outside environment. It consists of phopholipids, integral/peripheral proteins and cholesterol. It can exo and endo cytose.
What is the difference between organelles and inclusions?
Organelles are intracellular organisms which are essential to life (e.g. mitochondria) whereas inclusions are dispensable and may only be present as transients (e.g. pigment, glycogen stores, lipid droplets)
What are the three main classes of cytoskeletal protein filaments? What are they each composed of?
- Microfilaments (composed of actin)
- Intermediate filaments (made of six main proteins)
- Thick filaments/Microtubules (composed of two tubulin proteins)
What do microtubules do in the cell and where do they come from?
Can be assembled/dissasembled
Originate from special organising centre called a centrosome.
Serve as the motorways network of the cell as two proteins (dynein and kinesin) attach to the microtubules and move along the,. They then associate with the membranes of organelles and drag them along this microtubule.
What do kinesin and dynein do with regards to ATP
Kinesin is an ATPase which moves towards the cell periphery.
Dynein is an ATPase that moves towards the cell centre. Important in cells with long processes such as neurones
What does the smooth endoplasmic reticulum do? What cells would contain a lot of SER?
Plays a vital role at the site of synthesis of lipids.Cells synthesising steroid hormones would contain a lot of this.
What are the three types of cell junctions?
- Occluding junctions
- Anchoring junctions
- Communicating junctions
What do occluding junctions do?
The link cells to form a diffusion barrier (prevent diffusion)
The appear as a focal region of close apposition between adjacent cell membranes
Also known as tight junctions of zonula occludens.
What do anchoring junctions do? There are 3 types!
Type 1: Adherent junctions: They link sub membrane actin bundles of adjacent cells.
Transmembrane cadherin molecules bind to each other in the extracellular space and, through link molecules, to actin of the cytoskeleton
Type 2: Desmosomes: Link submembrane intermeediate filaments of adjacent cells. They are very common in the skin, where they provide mechanical stability.
Type 3: Hemidesosomes: These link sub membrane intermediate filaments of a cell to the extracellular matrix through transmembrane proteins.
What is a junctional complex?
Close association of several types of junctions found in certain epithelial tissues.
What are communicating junctions?
- Allow selective diffusion of molecules between adjacent cells.
- Often called gap junctions
- Each junction is a circular patch studded with severe; hundred pores.
- Pores produced by connexon proteins
- Found in epithelia, some smooth muscle and cardiac muscle where it is need for spread of excitation.
What is the use of intermediate filaments in pathology?
In identifying the primary origin of tumours
What is the perinuclear cistern?
The area between the inner and outer nuclear membranes
What is euchromatin?
DNA that is actively undergoing transcription
What is the heterochromatin?
DNA is condensed and not undergoing transcription
What does the small subunit of RNA do?
Binds ribosomes
What does the large subunit of RNA do?
Catalyses the formation of peptide bonds
What does the golgi apparatus do?
Modification and packaging of macromolecules synthesised in the ER.
What are cristae?
Inner membrane fold of mitochondria
What are intracellular junctions?
Specialised membrane structures which link individual cells together. Prominent in epithelia
How is endocytosis most often mediated?
By a receptor
How does phagocytosis work?
Bacteria or lerger particle binds to cell surface and triggers receptors which then cause extensions of the cell to engulf it forming a phagosome. It then binds with a lysosome carrying digestive enzymes
What is H & E staining?
Haemotoxylin (a basic dye that stains acids purple ) and Eosin (an acidic dye that dyes bases pink) are added so that cells can be seen under a microscope
What colour is DNA in an H &E preparation?
Purple
What colour are most proteins stained with H & E?
Pink
What are the four basic tissue types?
Epithelium
Connective tissue
Muscle
Nervous tissue
What do epithelia do?
Cover surfaces of the body or line hollow organs
What does connective tissue do?
Forms the framework of the body
Is adhesions between epithelial cells weak or strong?
Strong
What is a basal lamina?
A basement membrane to which all the cells are attached. It is a layer of extracellular matrix components at the basal surface
Are epithelial cells vascularised?
No
How do epithelial cells get nutrients?
They must diffuse from capillaries in underlying tissues across the basal lamina
Are epithelia polar?
Yes
What does psuedostratified mean?
Tissue appears to have multiple layers but it is actually all in contact with the basal lamina
What is a brush border?
Prominent microvilli on the epithelium
How do endocrine glands secrete their products?
Towards the basal end of the cell and through into the vascular system
How do exocrine glands secrete their products?
Towards the apical end of the cell either into the lumen of an internal space, into a duct or onto the surface of the body.
What kind of glands are ductless?
Endocrine
What counts as soft connective tissue?
Tendons, ligaments, mesentery, dermis of the skin
What is the type of connective tissue determined by?
The types and relative amounts of the cells and extracellular matrix
What are fibroblasts?
Widely distributed cells that produce and maintain the extracellular matrix.
How does cartilage receive nutrients?
It is avascular so has to receive nutrients from adjacent tissues by diffusion through its matrix
What are the three types of cartilage?
Hyaline
Elastic
Fibrocartilage
What is the most common type of cartilage and where do you find it?
[Hyaline cartilage] Articular surfaces Tracheal rings Costal cartilages Epiphyseal growth plates
What type of bone makes up the shaft/diaphysis?
Outer, dense, cortical bone
What sort of bones occupies the ends of bones(epiphyses)?
Cancellous/trabecular bone
What is canecellous bone?
A fine meshwork of bone that looks like the inside of an aero bar!
How is force produced in muscle cells?
The movement of actin over myosin fibres
What are the three major types of muscle tissue?
Smooth
Skeletal
Cardiac
Describe a typical skeletal muscle fibre
Giant, multinucleated, cylindrical cell. Nuclei are elongated and at the cell periphery
Are cardiac muscle cells single or multi nucleated?
Single, central nucleus
What des nervous tissue consist of?
Neurones and glia(support cell)
Is there more glia or neurones?
Glia
What is nervous tissue surrounded by in the CNS?
Meninges
What is nervous tissue surrounded by in the PNS?
Epineurium
What are the three types of neurone?
Bipolar, unipolar, multipolar
What are the main glia of the CNS?
Astrocytes (ion transport, support)
Oligodenrocytes (produce myelin)
Microglia (immune surveillance)
What are schwann cells?
The principle glia of the PNS, they produce myeline and support axons.
Why are the salivary gland ducts striated?
to allow for the secondary modification stage of saliva production
What are the four major layers of the digestive tract (lumen going out)
- Mucosa
- Submucosa
- Muscularis externa
- Serosa or adventitia
What three parts is the mucosa split up into?
- Epithelia
- Lamina propria
- Muscularis mucosae (thin layer of smooth muscle)
What is the submucosa?
Loose connective tissue
What is the muscularis externs?
Two layers of smooth muscle (inner circular layer and outer longitudinal layer
What kind of mucosa lines the small intestine?
Absorptive; simple columnar epithelium with tubular glands
What kind of mucosa lines the stomach?
Secretory: Simple columnar epithelium with tubular glands
what is the longitudinal smooth muscle in the large intestine called?
Teniae coli
Where about in the gut wall do ganglia live?
Between the two muscle layers that make up the muscular is extern
What are the spaces for blood flow in the liver called?
Sinusoids
What is the kidney epithelium called?
The renal corpuscle
What are neutrophils, eosinophils and basophils collectively called?
Granulocytes
What are the three layers of a muscular artery?
Tunica intima
Tunica media
Tunica adventitia
What separates the tunica media and the tunica adventitia?
External elastic membrane
What is the composition of arterioles
One or two layers of smooth muscle in their tunica media and almost no adventitia
What are capillaries composed of?
Endothelial cells and a basal lamina
What are pericytes?
Connective tissues that have contractile properties
What are the three types of capillaries?
Continuous
Fenestrated
Sinusoidal
What are fenestrated capillaries?
Have small pores (e.g. seen in gut mucosa)
What are sinusoidal capillaries?
Have large gaps e.g. in bone marrow
When do post capillary venules just referred to as venules?
When they begin to acquire smooth muscle cells in a tunica media layer
What are valves are extension of?
The tunica intima
What are the densest blood cells?
Red blood cells
What are erythrocytes?
Red blood cells
What is the life span of an erythrocyte?
about 4 months
What do neutrophils do?
Circulate the blood in an inactive state but if stimulates the enter the tissue and act as phagocytes
What colour does the cytoplasm of a eosoniphil stain?
Red
What is the nucleus of a eosoniphil like?
Bilobed
What do eosinophils do?
Contain hydroltic enzymes and they are important in inducing and maintaining inflammation (in allergic reaction and asthma especially!)
Also importnat in parasites
What are the rarest of the granulocytes?
Basophils
What colour in the basophilic cytoplasm?
Purple
What do the granules of basophils contain?
Histamine, heparin and other inflammatory mediators
What do basophils do?
Act as effector cells in allergic reactions. High affinity IgE receptors in their cell membrane are directed against a particular antigen and when they bind to this they degranulate reeling the inflammatory mediators (seen in hay fever, asthma etc)
Where are macrophages particularly found?
Loose connective tissue
What is the largest cell circulating in the blood?
Monocytes
What are monocytes?
Precursors of tissue macrophages
Do platelet cells have a nucleus?
No
What do platelets do?
Adhere to the site of damage and aggregate and degranulate/ The also activate the production of fibrin which participates in clot formation
What is a megakaryocyte?
Giant cells found in the bone marrow?
