Body Basics Flashcards
cell membrane
lipid bilayer containing cholesterol for stability and various proteins, in contact with cytoplasm, intercellular space and extracellular matrix
glycocalyx
molecules for cell-cell recognition, communication and adhesion
ECM
network of molecules (secreted by cells) that provides structural support, adhesion and communication to surrounding cells eg. Plasma is the ECM of blood
membranous organelles
membranes create cell compartments or separate processes
examples of membranous organelles
nucleus, mitochondria, rough and smooth endoplasmic reticulum, Golgi apparatus, lysosome, peroxisome
examples of non membranous organelles
ribosomes, flagella, cilia, centrosomes
cytoskeleton components
actin microfilaments, tubulin microtubules, intermediate filaments
function of actin microfilaments
cell movement, cell shape changes, microvilli structure
function of tubular microtubules
structural support, intra/extracellular transport, spindle in cell division
function of intermediate filaments
membrane support, localisation of organelles
kinesin motors
structures that carry organelles along microtubules/nerves using ATP hydrolysis
endocytosis examples
- Phagocytosis- cell membrane invaginates to engulf large molecules in a phagosome
- Receptor mediated (specific) endocytosis- clathrin forms a coat with deforms cell membrane to produce a vesicle in which molecules are taken into the cell eg. Insulin, LDL
- Non-specific endocytosis- a liposome containing large molecules fuses with lipid layer and contents are released into cell
exocytosis examples
- Constitutive secretion= newly synthesised cell membrane components (released from Golgi in lysosomes) fuse with CM randomly
- Regulated secretion= hormone stimulates above process
4 major tissue groups
epithelia, connective, nervous, muscle
epithelia functions
- Functions= exchange, transport, protection, secretion
- Form boundaries between environments and must be crossed by substances entering or leaving internal environment
what is epithelia formed from?
all 3 embryological layers
epithelia tissue general structure
- Highly cellular (regenerate rapidly due to friction) with little ECM and avascular so substances must diffuse to and from blood
- Cells are polarised, apical surfaces have microvilli to maximise surface area and bases have basement membranes for mechanical support
simple epithelia
one layer
shapes of epithelial cells
squamous, cuboidal, columnar
simple squamous cells examples and function
functions: filtration, diffusion, osmosis and secretion (little protection as it is thin)
examples: heart lining, blood vessels, lymphatics, alveoli
stratified cells function
protection due to regenerative capacity and multiple layers
cuboidal and columnar tissue function
secretion (bigger cells have more space to synthesise) and absorption (except stratified squamous)
simple cuboidal cells examples
Ovary, pigmented layer of retina, kidney tubules
simple columnar examples
GI tract lining, gall bladder, fallopian tubes
stratified cuboidal cells
Ducts of sweat glands
stratified squamous cells
Skin (keratinised), mouth/oesophagus (non keratinsed)
stratified columnar cells
Urethra lining, large gland ducts
glands
epithelia that secrete and store products like hormones
goblet cells
unicellular glands
endocrine glands
ductless so hormones are released directly into extra cellular fluid or blood to travel to target organs
exocrine glands
secrete products through a duct onto epithelium
3 types of exocrine glands:
- Merocrine- secretory product released from glandular cell in exocytosis
- Apocrine- vesicle containing products is secreted from glandular cell
- Holocrine- glandular cell dies and become secretory product
how are epithelial cells tightly associated?
intracellular junctions
tight junction structure and function
made of occuludins- interlocking protein links fuse membranes to give small intercellular space that limits permeability between cells
gap junction structure and function
connexons (protein tubes) allow transport between cells)
desmosome junction structure and function
cadherins (cell adhesion molecules)- gives stability to tissue
connective tissue function
support, load-bearing, protection, binding and transport
- not inert but responds to environments
- poor repair potential
basic structure of connective tissue, fluid and support
- Actual connective tissue = fat, ligaments
- Fluid= blood, lymph
- Supporting= bone, cartilage
Structure of Connective Tissues
- Extensive ECM for structural and biochemical support and few cells
- Through ECM, varying compositions of interstitial fluid, nerves, cells and capillaries
- Load bearing, dense tissues like cartilage have low vascularity while loose tissue like adipose have high vascularity
structure of ECM in connective tissue
Framework of extracellular fibres (collagen, elastin fibres and reticular fibres) with ground substance (proteoglycan molecules) filling gap between famework and any other structures present (cells, nerves, blood vessels and fluid)
collagens, elastic fibres, reticular fibres functions in connective tissue
- Collagens= tensile strength
- Elastic fibres= elasticity
- Reticular fibres= thinner and branching
integrins
proteins that signal between ECM and metabolic systems, allowing it to react to its environment
proteoglycans
highly hydrated molecules allowing compressive strength
