2: Cells, tissues and skin Flashcards
List some features common to all cells
- plasma membrane
- cytoplasm
- nucleus
in order to become more specialized for their unique role, cells, gain individual structures that lead to specific functions. - specific genes get turned on and off.
Describe cytoplasm
Structure= waterly fluid
Function= suspend organelles and maintain cell structure.
composed of= cytosol or ICF
contains; organelles and dissolved nutrients and proteins.
Describe the nucleus
Largest organelle
Function= houses DNA (contains the instructions for cell and protein synthesis)
“The control center”
Describe ribosomes
Function= site of protein synthesis
- adds amino acids together to form a long protein strand.
Free ribosomes= float around in cytosol/ICF and produce proteins for use inside the cell.
Membrane-bound ribosomes= attached to the endoplasmic reticulum produce proteins for export
Describe the endoplasmic reticulum
Structure= interconnected tubes continuous with the nuclear Function= synthesis, storage, transport, detoxification
Describe the rough endoplasmic reticulum (RER)
looks rough due to the presence of ribosomes. ER turns the amino acid chains produced from the ribosomes into the functional protein which it sends to the golgi apparatus.
Describe the smooth endoplasmic reticulum (SER)
no ribosomes attached. Synthesis of lipids and steroids hormones, storage of calcium ions
Synthesis and export of protein by RER
Cistern= body of water (sytoplasm)
1= protein is synthesised on the ribosome then migrates through the RER cistern.
2. the protein folds into its functional shape. short chains of sugar may be attached to the protein.
3. protein is packaged in tiny membrane sac called transport vesicles
4. The transport vesicle buds from the rough ER and travels to the Golgi apparatus for further processing.
Describe the golgi apparatus
Structure= flatternwd sacs Function= modify, concentrate and package proteins and lipids
forms vesicles and distributes them;
- within the cell
- move and become inserted within the plasma membrane
- move to the plasma membrane for the contact to be exported out of the cell by exocytosis
Describe mitochondria
“power house”
Structure= bean-shaped with enzymes on the surface of the inner membrane.
Function= cellular respiration- releases energy in the form of ATP
Enzyme outside of folds carry out a chemical reaction that break down nutrients from food and converting them into ATP.
Describe Lysosomes
“the demolition crew”
Structure= membrane-enclosed spheres that contain lysosomal enzymes.
Function= digest biological material including proteins and cell debris, dispose of invading bacteria, virus and toxins and recycle molecules
Describe the cytoskeleton and its three parts
A network of rods running through cytosol which act as a skeleton of the cell
Three types
1. microfilaments: thinnest, Structure= made up of a protein called actin.
Function= contract to make cell move.
2. intermediate filaments= resist pulling on call
3. Microtubles=
Structure= long, hollow, rigid.
Function= Determine the overall shape of cells involved in cell division and intracellular transport.
List the 3 types of cellular extensions and describe them.
Cilla- moving, on top of cells. sweep like waves to move materials across the surface.
Flagellum- single, long tail on bacterium and sperm. WHips for movement
Microvilli- finger-like extensions of the plasma membrane that project from cell surface increasing area.
Describe the characteristics of the plasma membrane
- thin and flexible boundary separating ICF and ECF
- consistency of olive oil.
- selectively permeable
- Allows for different chemical compositions between ICF and ECF to maintain homeostasis.
Explain the characteristics of the phospholipid bilayer
Hydrophilic phosphate head (polar)
Hydrophobic lipid tail (nonpolar)
all hydrophobic tails face the air and hydrophilic heads face the water.
Describe the plasma membrane structure
- double layer (bilayer) of phospholipids.
- Hydrophilic head face ECF and ICF (watery)
- Hydrophobic tails face towards each other creating a lipid core
this self-orienting property ensure molecules stick together
Explain the relationship between lipid and water solubility and repletion from the membrane core
lipid-soluble substance= water insoluble
- not repelled by the lipid core of plasma membrane
Water-soluble substance= lipid insoluble
- repelled by the lipid core of plasma membrane
List the 4 components of the plasma membrane
1- phospholipids
2- proteins (integral and peripheral)
3- cholesterol (membrane stability)
4- carbohydrates (“name or ID tages”)
Explain the two proteins of the membrane
Peripheral proteins
- not embedded- loosely attached to integral proteins or float free.
function= plasma membrane support, enzymes or motor function
Integral proteins
- embedded within the plasma membrane and span entire membrane
- classified as channel or carriers for substance transport (substance specific)
- substance-specific
- act as enzyme receptors
List the two-channel proteins (integral)
Leakage channels
Gated channels
Describe leakage gated channels
always open at both ends
e.g. substances that use them: water (aquaporin channel) and ions such as Na+ and K+
Describe gated channels
open at one end and can open and close at the other end. there are three types - mechanically gated - chemically gated - Voltage-gated
Describe carrier proteins
- transform shape to allow substances to pass.
- transport lipid insoluble or to large substances
e. g. glucose, amino acids
Define the term concentration and the concentration gradient gradient
concentration= measure of the amount of substance in an area
- high concentration= high number of a substance compared to other area and vice verse
The difference in the concentration of a particular substance between 2 different areas.
Define equilibrium
equal space between substances (state of stable conditions)
no net movement
Define diffusion
the movement of a substance from an area of high concentration to an area of low concentration. (down/along the concentration gradient)
List factors affecting rate of substance movement
- concentration gradient (the increased difference=increased speed)
- Size of substance (small= move faster)
- temperature (warmer faster)
List the 2 types of transport
1- passive transport
2- active transport
Describe passive transport
- requires no eneergy
- substances move down the concentration gradient
- includes; simple diffusion, facilitated diffusion and osmosis
Describe active transport
- requires energy (ATP)
- substances move up the concentration gradient
- includes; primary active transport with Na+/K+ ATPase pump
Explain simple diffusion
- unassisted transport of lipid-soluble or very small substances across the plasma membrane down its concentration gradient.
- continues until equilibrium is reached
- Lipid soluble substances move by simple diffusion
e. g. O2, CO2, fats, steroid hormones and alcohol
Explain facilitated diffusion
- assisted transport of large lipid insoluble substances from high to low across the membrane.
- Uses integral proteins
- for large or lipid insoluble substances
e. g. glucose, Na+ and K+
Explain osmosis
= the net movement of water (solvent) through a selectively permeable membrane from an area of more water (less solute) and an area of more water (less solutes) when the solute can not pass through the membrane (impermeable)
- water can move directly through bilayer (due to size, despite being lipid insoluble) or through channel proteins called aquaporins
remember osmosis looks at the movement of water from an area of high to low (when solute cant pass membrane). So this means it moves from low solute to high solute to dilute it.
Explain what diffusion and osmosis would look like through permeable and impermeable membranes
through a permeable membrane, water and solute would reach equilibrium.
Through an impermeable membrane, water would reach equilibrium but solute wouldn’t not.
Explain active transport
When substances move against their concentration gradient (i.e. from low to high), the cells uses energy ATP
- uses carrier proteins called Ma+/K+ ATPase pump
- allows for maintenance of concentration differences on each side (import for RMP)
Define exocytosis
transport process that moves substances to large for internal proteins out of the cell
- e.g. products from Golgi apparatus
Define endocytosis
transport process that moves substances to large for internal proteins into of the cell
- by phagocytosis
Define tonicity
the ability for a solution (fluid outside the cell) to affect the shape of a cell by altering the cells internal water volume (ICF)
- determined by the solutions surrounds and concentrations
Define isotonic tonicity
when an isotonic solution has the same water and solute concentration as the ICF.
- no change in shape
- maintain homeostasis of cell
Isotonic solution is what % saline
9%
Define Hypotonic tonicity
the solution has a lower concentration of impermeable solutes than ICF therefore a higher amount of water than the cell
Hypo= a high amount of solutes in the cell so the water rushes in to dilute it.
lyse= grow to an O
Define Hypertonic tonicity
the solution has high concentration of solute so ICF flows out of cell causing it to create.
Define resting membrane potential
potential energy (called voltage and measured in volts) that exists across the plasma membrane resulting from separating oppositely charged ions by the plasma membrane resulting from separating oppositely charged ions by the plasma membrane
Which side of the membrane has K+ and which has Na+
K+= ICF (K+ ill go to doolies) Na+= ECF (Na+ this is bad im leaving)
membrane has more K+ leakage channels so more K+ moves out then Na+ in
this creates an unstable membrane potential
How is a resting membrane potential generated?
- mainly by the movement of K+ ions from ICF to ECF through K+ leakage channels in plasma membrane leaving the outside of plasma membrane positive relative to the negative side.
How is resting membrane potential maintained
via ATPase pumps that sends
3x Na+ ions out
2x K+ ions in
active transport: requires ATP
this maintains the concentration gradient for ions to continue to diffuse through the leakage channels
Average resting membrane potential
-70mV
Identify 4 primary tissue types that all originated from stem celled
1- epithelial tissue
2- nervous tissue
3- Connective tissue
4- Muscle tissue
Describe properties of nervous tissues
- internal communication that transmits electrical signals to regulate and control body function
location: brain, spinal cord, and nerves - composed of neurons and supporting cells
function: communication
Describe properties of muscle tissues
- contracts to cause movement
muscles can: - attach to bones (skeletal)
- Be in the heart (cardiac)
- on walls of hollow organs (smooth)
composed of muscle cells that contractile microfilaments - specialised for contraction to allow movement
- three types of muscle
skeletal muscle- voluntary skeletal movement
cardiac muscle- involuntary and found in heart. - smooth muscle involuntary in blood vessels, guts, bladder, uterus
Describe properties of epithelial tissue
forms boundaries between different environments, protect, secretes, absorbs, filters.
e.g. skin surface (epidermis)
the lining of GI tract organs and other hollow organs
- sheet of cells that can cover the body, line internal organs form glands.
- anything that us exposed to the external environment is covered by epithelium so forms boundaries between different environments.
Describe properties of connective tissue
supports protects, binds other tissues
e.g. bones, tendons, fat, and other soft padding tissue
describe the structure of epithelial tissue
- composed of epithelial cells that are close together to form a sheet.
- these cells have one free surface and one attached to the basement membrane
- lack blood vessels (avascular)
- O2 and nutrients are delivered via diffusion from surrounding tissues
- contains neve cells for innovation
- susceptible to damage but can regenerate quickly
List 2 structural adaptations to epithelial tissue
Cilia: hair like cellular extensions that propel substances
Microvilli: finger-like extensions to increase surface area
what are the two classifications by layer ao epithelial cells
1- simple
- single layered
absorption, secretion, filtration
location= lungs, kidneys, digestive tract
2- stratified
- multiple layers of cells stacked on top of each other
protection
location= high abrasion areas (skin mouth )
Classification of epithelial cells by cell shape
squamous: flattened and slace like
Cuboidal: box like
Columnar: tall and column shape
Describe connective tissue
- connecting tissue of the body
most abundant and widely used of all tissue types
List the connective tissue types
1- CT proper: loose and dense
2- cartilage
3- Bone
4- Blood
What are the three characteristics of all CT
- specialised cells
- ground substance
- protein fibres
CT varies greatly in appearance with many different types of cells
Key property of CT
has large expanses of extra cellular matric and few cells.
Describe CT’s extracellular matrix
- nonliving composed of ground substance and protein fibers
- holds large volumes of ISF
- can bear weight and withstand great tension
Describe 3 types CT protein fibres
collagen fibres= tough w/ high tensile strength
Elastic fibers= long thin fibers for stretch and recoil
reticular fibers= short fibers continuous with collagen fibers
Explain the CT specialised cells immature and mature names
blast= immature Cyte= mature CT proper= Fibroblasts, fobrocytes Cartilage= chondroblasts, chondrocytes Bone= osteoblasts, osteocytes Blood= haematopoietic stem cells (blast cells), erythrocytes (RBC) and leukocytes (WBC)
Name some other cells found in CT
- RBC
- WBC
- adipocytes (fat cells: store aft)
- macrophages
- mast cells
Summaries the properties of Connective tissue proper
- broken into 6 sub classes of loose and dense connective tissue
- contains fibroblasts and fibrocytes
- loose CT characterised by loose arrangement of fibers and large amounts of ground substance
- dense CT characterised by closely packed bundles of fibers, little ground substance and poorly vascularised
- one class of CT proper is adipose tissue which contains adisotites
function= support, binding, storage and insulation
Summaries the properties of cartilage
3 types: hyaline, elastic and fibrocartilage
- cartilage that has qualities between dense CT and bone
- ECM up to 80% water
- consists of collagen and some elastic fibers so can withstand tension and compression
- contain chondroblasts and chondrocytes
- lack nerve fibres and is avascular
function= support and absorption compression
Summaries the properties of bone
- consists of abundant collagen fibers
- matrix is hard due to calcium phosphate crystals
- contains osteoblasts to produce organic portion of matrix
- osteocytes resorb bone as needed
- contain blood vessels and nerve fibers
Function= support, protection and storage
Summaries the properties of blood
- fluid within blood vessels
- consists of blood cells surrounded by matrix called plasma
- contains erythrocytes (RBC), leukocytes (WBC) and platelets
Function: transport substances throughout the body
What part of skin are each tissue type in?
stratified squamous, epithelial tissue= hypodermis and dermis
Connective tissue= dermis and mypodermis
smooth muscle tissue= arterioles
nervous tissue= skin with nerves
List the three layers of the skin
epidermis- outer epithelial layer
Dermis- a deep supporting layer of connective tissue
Hypodermis- a subcutaneous layer of connective tissue and adipose
Explain some features of the epidermis
- avascular
- oxygen and nutrients diffuse into cells
- tightly joined cells create sheet to prevent substances from moving through spaces between the cells= great barrier
cells are constantly dying and being shed then dead cells are replaced.
cells renewed 25-45 days
List the levels of the epidermis from most superior to least
Stratum Corneum Stratum Lucidum Stratum Granulosum Stratum Spinosum Stratum Basale
Describe features of the stratum corneum
- 20-30 layers thick dead keratinised flattened keratinocytes
- continuously shed
- protective barrier (abrasion, dehydration, penetration)
the cells flatten and die as they get up to the surface
Describe features of the stratum basale
- single layer of dividing epidermal stem cells - produce a new keratinocyte above the stem cell
- push older cells towards surface
- also contains melanocyte (produces pigment)
What 5 cell types compose the epidermis
- stem cells: divide
- keratinocyte: predominate cell of skin, produce keratin
- Melanocyte: produce melanin
- Merkel cells (tactile): touch receptors
- Langerhans cells/dendritic cells (macrophages): active immune system
Explain parts of the dermis
- consists of connective tissue
- includes macrophages and fibroblasts
- fibroblasts produce collagen and elastic fibers: provide strength and flexibility
contains
- blood vessels
- nerves + sensry receptors
- glands (sweat and sedaceous- produce sebum)
- hair follicles
Purpose of the hypodermis
- consists modly of adipose tissue function= - anchors skin to underlying tissue - stores fat - shock absorber - insulator
What are the 6 function of the skin
1- Protection - physical - chemical - Biological 2- Sensation 3- Metabolic function 4- Excreation 5- Blood reservoir 6- Temperature reulation
Function of skin- Protection (physical/mechanical)
- tightly joined epidermal cells, keratin and oily secretions blocking most water and water-soluble substances
Function of skin- chemical barriers
- low pH secretion preventing bacteria from multiplying
- defensins (natural antibiotic) secreted by skin cells to kill bacteria
- melanin protects DNA in underlying cells fro, UV da,age
Function of skin- biological barriers
- macrophages engulf and dispose of microorganisms tat manage to penetrate the epidermis
Function of skin- sensation
Dense network of nerves
- controls blood flow (vessel diameter)
- controls glandular secretion (e.g. sweat)
Collects sensory info:
- pain (nocioceptors)
- Temp (Thermorecpetors)
- touch, pressure and vibration (mechanoreceptors)
Other function
metabolic function- synthesizes Vitamin D
Excretion- nitrogenous wastes and salts are excreted in sweat
Blood reservoir- can hold 5% of bodies blood
- dense blood vessel network
- amount of blood flow through these blood vessels can be regulated by the diameter of the vessel
e. g. for temp control
Function of skin- Temp reulation
- vaso dilation and contriction
- sweat glands
monitored by thermoreceptors and thermoregulatory centre
describe the effect of ageing on skin
skin thins- more cells lost then formed
wringles form= decreased fibroblasts which lead to lack of collagen and elastin
skin dies and itches= decreased sweating and gland activity
other chnages- loss of hair, grey hair, colder skin, thicker nails
Describe the three membranes of the body
Cutaneous membrane
- skin, exposed to air and is dry
Mucous membrane
- lines body cavities that are outside of the body.
- In digestive, respiratory and urogenital tracts
- we membrane due to secretions
Serous membrane:
- line closed ventral body cavities.
- secretes a clear serous fluid to lubricate surface.
- wet membranes that are not exposed to external environment
Two main processes of tissue repair
- regeneration ‘- replaces destroyed tissue with the same kind of tissue
- can be restored to normal if the damage is minor or epidermal stem cells present to regenerate lost tissue. - fibrosis
- replaces destroyed tissue with scar tissue
- damage that includes the dermis leads to repair by fibroblasts
- scar tissue does not have any of the same qualities as the tissue before the injury
What are the 3 stage of tissue repair
stage 1: inflammation
Stage 2: organisation or proliferation
stage 3: maturation or remodeling
Explain stage 1: Inflammation
Function: prepares the wond for repair, eliminated invading microorganisms and removes debris and dead tissue.
- damaged cells release inflammatory chemicals that cause inflammation
- signs of inflammation: swelling, redness, pain and heat
- blood vessels become more permeable: fluid released into are included;
macrophages: enjulf debris/invading microorganism
Clotting protein: produce blood clots to stop blood loss, minimise and electrolyte loss, holds wound together and prevent new invading microorganism. - clot on surface dries and forms a scab
Stage 2: Organisation or proliferative stage
Function: extracellular matrix synthesis including collagen and restore a blood supply.
- blood clots replaced by granulation tissue- comprised of capillaries that grow across the wound to restore blood supply, bring oxygen and nutrients required for healing
- fibroblasts-> produce collagen fibres that bridge the gap
- macrophages-> engulf cell debris, invading microorganisms and blood clot
epithelial stem cells multiply and migrate over the granulation tissue.
Stage 3: maturation or remodeling
Function: complete permanent skin repair
- collagen laid down in stage 2 is remodeled and contracts to pull wound edges together.
- scar is avascular
- if stemn cells are present naer cell they can regenerate epitheliaum
- repair predominantly by fibrosis
- scar tissue= thouh but not elastic or flexible, no hair, sweat or oil glands
Skin damage during burns
- may lead to protein denature , cell death, tissue damage
- loss of skin function
immediate threat to life resulting from fluid loss due to loss of physical protection of skin. - leads to dehydration, electrolyte imblance then renal shutdown and circulatory shock infection via microorganisms.
Burns classification
superficial- 1st degree= epidermisi
Partial thickness- 2nd degree; epidermis and part of dermis
Full thickness- 3rd degree: entire thickness of skin
Treatment of full thickness burns
usually require gerafts
as many components of skin are lost so it cant heal and have adequate function without stem cells especially.
