Histology Flashcards
The plasmalemma is known by which other name?
Cell membrane
Many proteins are anchored into the cell membrane, what functions may they have?
. Receptors
. Enzymes
. Channels
. Transporters
What are the three types of filaments that make up the cytoskeleton of a cell?
- Microfilaments
- Intermediate filaments
- Microtubules
What are the smallest type of filaments that make up the cytoskeleton?
Microfilaments
(approx 7nm diameter)
Microfilaments are composed of what?
Actin
There are more than 50 classes of intermediate filaments, what can each class give an indication of?
Origin of the cell in the body
(this can help when locating tumours)
What are microtubules composed of?
Alpha and beta tubulin subunits
Which two proteins can use microtubules as a transport network and which direction does each travel?
. Kinesin - An ATPase that transports compounds towards the cell periphery
. Dynein - An ATPase that transports compounds towards the cell centre
The nucleus is surrounded by an _______ and ________ membrane.
Inner and outer
The outer membrane of the nucleus shares a common border with what?
The rough endoplasmic reticulum
What is between the inner and outer nuclear membranes?
The perinuclear cisterna
There are three types of RNA, which two are transcribed and which is transcribed in the nucleolus
Nucleus - mRNA, tRNA
Nucleolus - rRNA
The nucleus contains two states of DNA, what are these states?
- Heterochromatin - DNA condensed and not undergoing transcription
- Euchromatin - DNA untwisted and undergoing transcription
Where are ribosomes formed?
Nucleolus
What two subunits make up a ribosome?
Small subunit - binds to mRNA
Large subunit - catalyses formation of peptide bonds
What are the two types of endoplasmic reticulum?
- Rough
- Smooth
What are polysomes?
Clusters of free ribosomes in the cytoplasm surrounding mRNA which is being transcribed
What is the role of the smooth endoplasmic reticulum?
Processing proteins after passage through the rough endoplasmic reticulum and also for the synthesis of lipids
What is the role of the rough endoplasmic reticulum?
The synthesis of membrane bound proteins or secretions.
It is also the site of glycoprotein formation
What is the role of the golgi apparatus?
The pakaging and processing of proteins for export to their destinations
The golgi apparatus is made up of many flattened sacs resembling plates, what is each sac called?
A Cisterna
How do proteins arrive at the golgi apparatus?
In transport vesicles from the smooth endoplasmic reticulum
What is the inner membrane of mitochondria called?
The cristae
This is folded to increase surface area
DNA can be found in which two locations within a cell?
- Nucleus
- Mitochondria - they have their own DNA
Which type of muscle will have many mitochondria and which type will have few?
. Many mitochondria - Slow twitch muscle - generally aerobic
. Few mitochondria - fast twitch muscle - generally anaerobic
What are intercellular junctions?
Structures specilaised to join cells into groups to form a functional unit
Where are intercellular junctions most prominent?
Epithelial Cells
What are the three types of intercellular junctions?
- Occluding
- Anchoring
- Communicating
Occluding junctions can have which other name?
Tight junctions
(or zonula occludens)
What do occluding junctions function to do?
Link cells together to form a diffusion barrier
What are the three types of anchoring intercellular junctions?
- Adherent
- Desmosomes
- Hemidesmosomes
Describe the function of anchoring adherent intercellular junctions
Actin in the cytoplasm is used to link adjacent cells together
Actin is bound to cadherin - a transmembrane protein which acts as an adhesive linking cells together
Describe the function of anchoring desmosome intercellular junctions
Intermediate filaments are used to join cells as they can bind with transmembrane proteins.
This can provide stablity in the skin
Describe the function of anchoring hemidesmosome intercellular junctions
Intermediate filaments are linked directly to the extracellular space with the help of transmembrane proteins which can anchor the filaments in place
What is a junctional complex?
This is when many types of junctions are used in close proximity
This is common in epithelial cells
Communicating junctions have what other name?
Gap Junctions
What are communicating junctions composed of?
A circular patch with many pores created by connexion proteins which make direct channels between cells
Communicating junctions allow for what between connected cells?
Selective diffusion and transfer of certain molecules
Communicating junctions are common in which tissue types?
- Smooth muscle
- Cardiac muscle (spread of excitation)
- Epithelial cells
There are 3 main ways in which substances can be transported across a membrane, what are these?
. Diffusion
. Protein pumps/channels
. Endo/exocytosis using vesicles (vesicular transport)
During endocytosis, material in the ___________ space can be engulfed by the cell forming an __________
Extracellular
Endosome
What is it called when a phagosome and lysome fuse?
A phagolysosome
When tissue is prepared for microscopy which chemical may be used to cross link proteins and maintain structure?
Formalin
What is added to tissues to give it structure before it is used for microscopy?
wax
What is a common dye used to allow differentiation in different cell parts?
“H & E”
. Haematoxylin (H) - a basic dye which binds to acidic molecules such as DNA or ribsomes causing a purple colour
. Eosin (E) - an acidic dye which binds to basic molecules such as cytoplasmic proteins causing a pinkish colour
What are the four basic tissue types?
. Epithelium
. Connective tissue
. Muscle
. Nervous
What is the basal lamina?
The extracellular matrix of components at the basal (underside) surface of epithelial cells.
Which type of cells are not vascularised and how do they aquire nutrients?
Epithelial cells
They acquire nutrients via diffusion from the basal lamina
What are the different epithelial cell shapes?
. Squamous (flat)
. Cuboidal (cube shaped)
. Columnar (cuboidal - tall and thin)
What are the names of epithelia based on the number of layers?
. One - simple
. Two or more - stratified
. Multiple layers - pseudostratified (all cells in contact with the basal lamina)
What are the three subtypes of connective tissue?
- Soft connective tissue
- Hard connective tissue
- Blood and lymph
What are the two types of epithelial gland?
- Endocrine (ductless) - product secreted towards the basal end of the epithelium and distributed into the vascular system - lots of capillaries will surround the glands
- Exocrine (ducted) - product secreted upwards towards the apical end of an epithelial cell
What are fibroblasts?
Cells that are widely distributed in the extracellular matrix helping to maitain it
What are chrondrocytes?
Cartilage Cells
Within the extracellular matrix there is ground substance, what is this?
A large space containing a gel-like substance made of huge polysaccharide molecules called glycosaminoglycan which are mostly bound to protein cores to form glycoproteins
What are the two types of soft connective tissue?
- Dense regular - densely pack collagen fibres in ordered alignment
- Dense irregular - densely packed collagen fibres running in many directions which resists breakage
What allows cartilage to be flexible?
The ground substance in cartilage is very hydrated allowing for this type of flexible stucture
How does cartilage receive nutrients since it is not vascularised?
Diffusion through its matrix
What are the three types of cartilage?
- Hyaline
- Elastic
- Fibrocartilage
What are the two types of bone which are distinct to the naked eye?
- Cortical bone - outer shell composing the shaft (diaphysis)
- Cancellous (trabecular) bone - inside of bone, an interconnected network of bone fragments that contains small holes and hollow sections
What are osteocytes?
Bone Cells
What are the three major types of muscle tissues?
- Smooth (involuntary)
- Skeletal (voluntary)
- Cardiac
What causes skeletal muscle striations?
The overlapping of actin and myosin filaments
What joins cardiac muscle cells together?
Intercalated discs
(gap junctions are common between cells)
Neurones in the CNS and PNS have a coating around them, what is this coating called in each area?
- CNS - Meniges
- PNS - Epineurium
Depending on the way the cell body is attached, neurones fall into which three categories?
- Unipolar - cell body attached in one place
- Bipolar - cell body attached in two places
- Multipolar - cell body attached in many places
What are the three types of glia?
- Astrocytes
- Oligodendrocytes
- Microglia
What is the function of astrocytes?
Provide support and contribute to ion transport
They also play a role in tissue repair after damage and aid by producing scar tissue by secreting the contents of their extracellular matrix
What is the role of oligdendrocytes?
To produce myelin
Microglia have what function?
To provide immune surveillance
What is the principle glia of the PNS and what is its function?
Schwann cells
Produce myelin and support the axons
Striated ducts are present in salivary ducts, what is their function?
They actively pump salt ions out of saliva ensure saliva remains hypotonic to red blood cells preventing water from inside red blood cells flowing into the saliva
What are the four layers of the digestive tract outwards from the lumen?
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
What is the mucosa in the digestive tract composed of?
. Epithelium - sits on the basal lamina
. Lamina propria - loose connective tissue
. Muscularis mucosae - thin layer of smooth muscle
What is the submucosa in the digestive tract composed of?
Loose connective tissue
What is the muscularis externa composed of in the GI tract?
Two thick layers of smooth muscle
. Inner circular layer
. Outer longitudinal layer
What is the serosa in the GI tract composed of?
Connective tissue
(can suspend or attach the digestive tract to other organs)
The outer longitudinal layer of muscle in the muscularis externa within the GI tract is not continuous, but instead found in 3 strips called what?
Teniae coli
What is the enteric nervous system?
The nervous system of the digestive tract allowing it to function independently with input from the autonomic nervous system
Within the liver, what comprised a portal triad?
- Hepatic portal vein
- Hepatic artery
- Bile duct
What does the exocrine pancrease function to do?
Produce digestive juices containing proteases and other breakdown enzymes as well as lipases and nucleases
What is the function of the endocrine pancreas?
It is covered in many receptors (islets of Langerhans) which produce hormones insulin and others to regulate blood sugar levels
What percentage of blood is composed of cells?
45%
What percentage of the cells within blood are red blood cells are what percenatge are white blood cells?
Red- 99%
White- 1%
What are the five main types of lymphocytes found in blood?
- Neutrophils
- Lymphocytes
- Monocytes
- Basophils
- Eosinophils
Arteries are made up of what three layers?
- Tunica intima
- Tunica media
- Tunica adventitia
In artery walls, the tunica media and tunica adventitia are separated by what type of membrane?
External elastic membrane
The walls of capillaries are composed of what?
Endothelial cells and a basal lamina
Why do veins have a wider lumen when compared with arteries?
They carry blood at a lower pressure
What factors aid the movement of lymph around the body?
- Smooth muscle in the walls of the body
- Hydrostatic pressure
- Compression of vessels by skeletal muscle contraction
Elastic arteries are so thick-walled that they require have their own blood supply, which vessels supply there arteries?
Vaso vasorum arteries
A capillary bed is made up of a network of what?
- Metarterioles
- Throughfare channels
- Capillaries
- Precapillary sphincters
What are pericytes?
Cells that surround the basal lamina or capillary endothelial cells
They have stem cell properties yet mostly aid contraction
What are the three types of capillaries?
1, Continuous
2. Fenestrated
3. Sinusoidal
Describe continuous capillaries
They are found inmuscle, nerve, lung and skin tissue
They are the least permeable of all capillaries and have intact walls
Describe fenestrated capillaries
They have small pores in their walls allowing larger molecules to pass though.
Commonly found in the gut mucosa, endocrine glands and the kidney
Describe sinusoidal capillaries
They have large gaps are are discontinuous
They are found in the liver, spleen and bone marrow
What do capillary networks drain into?
Post-capillary venules
At which point is a capillary termed a venule?
As soon as there is smooth muscle in the walls
Why do the largest veins have a thich layer of tunica adventitia?
It aids in the support of a physically larger structure
What two different classes of white cells are found in the blood?
- Granulocytes
- Agranulocytes
What is the average lifespan of a red blood cell?
120 days
Old red blood cells are removed from circulation by which two organs?
Liver and Spleen
What is the most abundent white cell in the blood?
Neutrophil
Eosinophils stain well with what dye?
Eosin (a red acidic dye)
Basophils stain well with which dye?
Basic dyes
(methylene blue)
Where does erythrocyte formation firstly occur?
Yolk sac during embryonic development
(after around 3 weeks of gestation)
At birth, what area of the body becomes the area of red blood cell formation?
Bone marrow
In adulthood only vertebrae, ribs, skull and proximal femurs retain haemopoiesis - the ability to produce red blood cells
What is an erythrocyte termed after RNA granules appear in its cytoplasm?
Reticulocyte
Describe the steps in the pathway of erythrocyte development
- Proerythroblast
- Basophilic erythroblast (early normoblast)
- Polychromatic erythroblast (intermediate normoblast)
- Orthochromatic erythroblast (late normoblast)
- Reticulocyte erythroblast
What are megakaryocytes?
Huge cells that allow for platelet formation
Plateletes will bud off from small sections of the cytoplasm
What happens to a megakaryocyte after many platelets have been produced from it?
It will undergo apoptosis
