Introduction to Histology Flashcards
What is the function of the plasma membrane?
To regulate the transport of chemicals between the outside and the inside of a cell
What is the basic structure of a plasma membrane? What is this described as?
- lipid bilayer
- made of many lipids, proteins and carbs
- semi-permeable membrane
- ‘fluid mosaic’ model
What is the concept of the ‘fluid mosaic’ model
- individual phospholipids can move in relation to each other
- forms a dynamic structure
- embedded with larger molecules like proteins
What is the general structure of phospholipids found in the bilayer? How do phopholipids behave in water?
- polar hydrophilic head
- non-polar hydrophobic tails
- in an aqueous environment, tails orientate themselves away from the water
- this forms the bilayer
What are the 4 different types of proteins that can be found on the plasma membrane?
Structural
Transport
Receptors
Proteins with enzymatic activity
What is the structure of centrioles?
- nine sets of 3 microtubules
- occurs in pairs
- in a pair of centrioles, individual centrioles are arranged perpendicular to each other
Where are centrioles found?
- in an area near the nucleus
- called the centrosome (cell centre)
What are the 2 functions of centrioles?
- organise microtubular network
- organise development of microtubules in cilia
What is the structure of the RER?
- network of tubules
- ribosomes dotted around
- vesicles
- flattened cisternae continuous with nuclear envelope
What is the function of the RER?
To process and fold proteins via glycosylation and structural changes
What is the structure of the SER?
- irregular network of tubes
- vesicles continuous with RER
- no ribsomes
What are the 2 functions of the SER?
- synthesis of lipids
- intracellular transport
How many subunits do ribosomes compose of?
2
What is the function of ribosomes?
It is the site of mRNA translation for protein synthesis
Where are the 2 possible places a ribosome can be found and what is the difference between the protein synthesis that occurs in both areas?
- either in cytosol (for cell protein synthesis)
- or attached to ER (for membrane/secretion protein synthesis)
What are the 3 functions of the golgi apparatus?
- modification of proteins, by addition of sugars
- proteolysis- activation of peptides
- sorting and packaging of macromolecules into vesicles for transport within the cell and for secretion
What is the structure of microtubules?
- hollow fibres
- formed from 2 protein subunits- alpha and beta tubulin, which join alternatively to form protofilament chains and arrange into groups of 13
- constantly forming and unforming within the cell
- grow out of the centrosome
- proteins used to stabilise it
What are the 5 functions of microtubules?
- intracellular transport
- present in cilia and flagella
- form cell cytoskeleton
- form filaments of mitotic spindle
- form centrioles and basal bodies
Which cell does not contain microtubules?
Red blood cells
What is the structure of intermediate filaments?
- intermediate in size between microtubules and microfilaments
- vary slightly according to the cell type they’re in
What are 2 examples of the variation of intermediate filaments found in cells?
- cells showing muscle differentiation contain desmin
- epithelial cells all contain cytokeratin
What are the 2 functions of intermediate filaments?
- provide mechanical support for the plasma membrane
- reinforce cells and organise them into tissues
What is the structure of microfilaments?
- composed of actin
- smallest proteins of cytoskeleton
- form crosslinked mesh below plasma membrane
What are the 3 functions of microfilaments?
- provide mechanical support to plasma membrane
- actin molecules form bundles which protrude membrane to form microvilli
- actin and myosin generate motion
What is the structure of microvilli?
- small finger-like projections
- found on apical surface of most epithelial cells
What does the number and shape of microvilli correlate to?
The absorptive capacity of the cell
What is the function of microvilli?
To increase the surface area of the cell
What is the structure of mitochondria?
- has its own DNA so can synthesise proteins
- double membrane
- folded into cristae
- fluid-filled matrix
What is the function of mitochondria?
Site for aerobic respiration and provides energy to cells via oxidative phosphorylation
Which cell does not have mitochondria?
Red blood cells
What is the structure of the nucleus?
-contains nucleoulus, nucleoplasm, pores and a nuclear envelope
What is the function of the nucleus?
Contains cell DNA and is the site of RNA transcription
What are the 2 functions of the nucleolus?
- site of transcription
- processing of rRNAs and their assembly into ribosomal subunits before export to cytoplasm
What does the size of the nucleolus depend on?
Depends on how metabolically active the cell is
What can be seen on a metaphase spread and what is it used for?
- can see fully condensed chromosome
- used for karotype analysis
Which stain is used for the metaphase spread and what colour does it produce?
- propidium iodide
- produces a red colour
What is epithelium?
- the covering outside the body
- lines many hollow organs
- made up of epithelial cells
What functions does epithelium have?
Secretory and absorptive functions
What are the 3 major types of cells that make epithelium?
Squamous
Glandular
Transitional
Where is squamous epithelium found?
- skin
- lining of hollow organs e.g. oral cavity, oesophagus, anal canal, vagina
How is squamous epithelium described?
- flat
- either simple (single layer of cells) or,
- stratified (many layers of cells)
Which cells line blood vessels?
Endothelial cells
Which cells line body cavities?
Mesothelial cells
What do glandular epithelial cells do?
Secrete hormones into the bloodstream -islets cells in pancreas secrete insulin Lining of some hollow organs -GI tract etc Make other substances -breast epithelium produces milk Absorb material -large bowel-lining cells absorb water and salts from bowel contents
What types of glandular epithelium are there?
-columnar and cuboidal
Which organs do transitional cells line?
Kidneys, bladder and the rest of the urinary tract
What are desmosomes?
Specialised junctions that join together layers of cells in squamous epithelium
What does the upper part of squamous cells contain, and what does this cause?
Keratin, makes the surface hard-wearing
What is the surface of the skin called and what is it made up of?
- called the epidermis
- made up of stratified squamous epithelium
What key property does transitional epithelium have?
-being able to stretch and recoil depending on urine volume
What is transitional epithelium resistant to?
The adverse effects of urine
What makes up the musculo-skeletal system?
-muscles, bony skeleton, tendons, joints
Which cells make up adipose tissue and what is their function?
Adipocytes (fat cells), they store fat
What are the 3 functions of adipose tissue?
- energy reserve
- insulation
- peripheral synthesis of some hormones
Where is adipose tissue found?
- immediately underneath the skin
- around some internal organs e.g. kidneys
Where is fibrous connective tissue found?
Within all organ systems except CNS
What type of tissue is found in the CNS?
Fibroblasts
What is the specialised function of fibrous connective tissue?
To make collagen
What is collagen?
- protein that’s secreted out of the cell into spaces between organs
- forms part of the extra-cellular matrix
- forms flexible but tough tissue
What does collagen help do to organs?
Helps to hold them in place within the body
What are the 3 different types of connective tissue?
- loose (areolar)
- dense irregular
- dense regular
What is the process of ossification?
Where osteoblasts convert cartilage/fibrous tissue into bone (a.k.a the process of bone formation)
What are chondrocytes?
Cells that synthesise extra-cellular matrix material (such as glycoaminoglycans) which make up cartilage and repair it
What is the purpose of cartilage?
Forms a low friction cover for bones where joints are formed
Where are synovial cells found and what is their purpose?
- found in joints
- purpose is to make joints fluid to allow easy movement and to cushion bones
What are chondroblasts?
Cells that secrete the major component of cartilage (extracellular matrix). Once they do this, they become less active and are now called chondrocytes
What are the three types of cartilage?
Hyaline cartilage
Fibrocartilage
Elastic cartilage
What does the classification of cartilage depend on?
Fibrous proteins
What is hyaline cartilage made up of? What is its function and where is it found?
- Type II collagen
- created as a temporary skeleton for bone formation
- found in joints and lungs
What is fibrocartilagecartilage made up of and where is it found?
- Type I and II collagen
- found in intervertebral discs and tendon attachment to bones
What is elastic cartilage made up of and where is it found?
- Type II collagen and elastic fibres
- found in ears, epiglottis and larynx
What are two examples of pathology in epithelial cells?
Squamous cell carcinoma
Breast cancer
What is squamous cell carcinoma?
- type of skin cancer
- exposure to sun causes damage to DNA in the nuclei of squamous cells
- can lead to uncontrolled cell division so more cells are produced than needed
What is breast cancer?
- type of cancer where breast epithelial cells undergo cancerous/malignant change
- invade through fatty connective tissue of the breast
What is an example of pathology in the musculo-skeletal system?
Inflammation of joints- Arthritis
Name a cause of Arthritis
Gout
What is gout?
- impaired ability to deal with uric acids so it sits in soft tissue and joints
- causing an inflammatory reaction with neutrophils entering the joint
- causes pain and swelling
Which joint does gout affect?
The first tarso-metatarsal joint
What is an example of pathology in muscles?
Myocardial infarction (heart attack)
What causes a myocardial infarction?
- build up of fatty deposits in the walls of blood vessels going to the heart
- means blood supple to the heart muscle is obstructed
- heart muscle cells then start to die
What is an example of pathology in the NS?
Diabetes
What does diabetes affect?
- blood vessels supplying various organise such as the eyes and kidneys
- sensory nerve endings
What are long-term complications of diabetes?
- lack of sensation in feet
- impaired vision
