Body Logistics Flashcards
What does homeostasis mean?
Homeo-same
Stasis-standing still
What type of equilibrium is homeostasis?
Dynamic equilibrium
What is homeostasis?
Maintaining a constant internal environment
What needs to be maintained in homeostasis?
Conc. of O2, CO2, salt, electrolytes Conc. of nutrients, waste products pH Temperature Volume/Pressure of body fluid compartments
Which technique does the body use to maintain homeostasis?
Feedback loops (positive and negative)
What is positive feedback?
A substance stimulates another substance, which in turn stimulates the fist substance. Amplification of an effect.
What is negative feedback?
Returning levels back to normal. One substance will inhibit another.
What are the types of glands?
Endocrine and exocrine.
What does an endocrine gland do?
Produce and secrete hormones into the blood.
What does an exocrine gland do?
Produce and secrete chemicals through ducts onto an epithelial surface e.g. Skin.
Examples of glands
Hypothalamus Adrenal Pituitary Parathyroid Thyroid Pancreas Gonads Thymus
What are the requirements for light microscopy?
Preserve tissue -e.g. In formalin
Embed tissue in substance that allows it to be sliced very thinly -e.g. In paraffin
Stain tissue so you can see cell components -e.g. Haematoxylin and Eosin (H&E)
How do Haematoxylin and Eosin stain samples?
H stains nucleus blue most strongly
E stains cytoplasm and extracellular matrix pink most strongly
What are the advantages/disadvantages of frozen section?
Adv- quicker (10mins vs. 16hrs)
Dis- lower technical quality
What is polarised light?
Light travelling in one direction
How many nanolitres in a microlitre?
1000
How many microlitres in a millilitre?
1000
How many decilitres in a litre?
10
What mass do you take to be the mass of a human?
70kg
How much of the human body by % is water?
60% (42L in 70kg person)
How much water is extracellular/intracellular?
1/3 is extracellular (14L in 70kg person)
2/3 is intracellular (28L in 70kg person)
Of the extracellular fluid in a 70kg person how much is interstitial and how much is in the blood?
Interstitial- 11L
Blood- 3L
What is haematocrit?
Proportion by volume of circulating blood that is red blood cells (40%)
What is the circulating blood volume?
5L-3L plasma, 2L RBC
What is the normal haematocrit?
40%
How often does the total blood volume circulate?
Once per minute
What do macrophages do?
Recognise foreign antigens and take them into the macrophage. It then breaks it down using lysosomal enzymes and gets rid of the debris. It often presents part of the antigen on the surface.
What do B lymphocytes do?
Naïve B cells sense the shape of a foreign antigen and produce antibodies with a complementary variable site to that antigen. Also B memory cells are produced, so that if the same antigen is found again an immune response can occur more quickly.
Where are B lymphocytes made?
Bone marrow
What type of response are B lymphocytes and macrophages part of?
Humoral
Where are T lymphocytes made?
Bone marrow, and mature in thymus
What do T lymphocytes do?
They create killer T lymphocytes which then dock next to cells infected with virus (or cancer cells) and kill them. Memory T lymphocytes are also made.
What type of response are T lymphocytes part of?
Cell mediated
What do T helper cells do?
They sense the shape of the foreign antigen displayed by a macrophage (and become activated). It then tells this shape to the B cells and activates macrophages. It also activates killer T lymphocytes.
What are monoclonal antibodies?
Antibodies that all originate from the same cell (hybridoma).
What is a hybridoma?
Fusion of B cell and myeloma (cancer cell)
What are some properties of hybridomas?
Immortal
Highly specific
What is an epitope?
A binding site found on antigens
What do antibodies do?
Bind to complementary antigens which stops them entering cells and stops them growing. It also groups them in one place so they can easily be killed by macrophages.
What is a conjugated antibody?
An antibody with a radioactive marker attached
How does autoradiography work?
A radioactive marker is injected into a live animal/cell culture
A histological section is coated with a photographic emulsion which shows molecules labelled with the radioactive marker
What is the typical magnification in light microscopy?
x1000
What is the distance between resolvable points in light microscopy?
0.2 micrometers
How does ultrasound work?
The transducer contains piezoelectric crystals which vibrate when an electric signal is applied which produces ultrasound waves. The ultrasound waves pass through the skin and into the internal anatomy. As the waves encounter tissues with different characteristics and densities they produce echoes which reflect back to the transducer. The piezoelectric crystals then produce an electrical signal which a computer converts into points of brightness on an image.
If an ultrasound wave has high frequency what qualities does it have?
Short wavelength
Good resolution
Travels quickly
Why does an electron microscope have a higher resolution than a light microscope?
Because it has a shorter wavelength
What is the typical magnification of an electron microscope?
x250,000
How does a transmission electron microscope work?
Only works in a vacuum (all samples are dead).
An electron beam passes through the sample and any beams that pass through are detected. Where beams pass through the sample this part of the image will be bright, where they don’t it will be dark.
What is freeze fracture EM?
Tissue is frozen to -160 degrees C and fractured by hitting with a knife edge. The fracture line passes through the plasma membrane exposing its interior which can then be imaged (in vacuum with EM)
How does a scanning electron microscope work?
Only works in a vacuum (dead sample). Electron beams are fired at the sample. They then reflect back from the surface and are received by a cathode ray tube.
What was MRI adapted from?
NMR
What is the function of an epithelial cell?
Separating the inside from the outside of the body and separating different environments of the body.
What are cell junctions?
They are found between adjacent epithelial cells and ensure the cells are tightly adhered to one another.
What are the 3 main types of cell junctions?
Tight junctions-firmly adhere adjacent cells to one another.
Desmosomes-strengthen the tight junctions and are resistant to stretching and twisting.
Gap junctions (communication junctions)-allow adjacent cells to talk to each other.
How are tight junctions made and what is their function?
The plasmalemma of adjacent epithelial cells are fused together. It forms a seal which stops molecules passing between the cells, so it must go through the epithelial cells.
How are desmosomes made and what is their function?
They are found just under or next to tight junctions. They strengthen the bond between cells. They are formed by proteins which are interlocked and connect the cells.
How are gap junctions made and what is their function?
They are found between adjacent cells and allow them to communicate with each other and coordinate functions. Proteins called connexons form small channels that allow ions and small molecules to move back and forth between cells. They allow messages to pass between cells.
What is the basement membrane?
It is the structural site for overlying cells and underlying connective tissue. It anchors down the epithelium to its loose connective tissue underneath.
How can cells attach to the basement membrane?
Hemidesmosomes:integrins connect the plasma membrane to the basement membrane. (Found in tissues subject to abrasion).
Focal adhesions: anchor intracellular actin filaments to the basement membrane. Integrins attach the actin filament complex through the cell membrane to the extracellular matrix. (Important in call movement e.g. Migration of epithelial cells in wound repair).
What are integrins?
They are transmembrane proteins that attach the cell cytoskeleton to the extracellular matrix and sense whether adhesion has occurred.
What are the 2 main functions of integrins?
Attachment of the cell to the ECM.
Signal transduction from the ECM to the cell.
(Also involved in immune patrolling and cell migration).
What is required for cell cultures to survive?
Provide nutrients, control pH, temperature and oxygen. Prevent bacterial contamination
How do you separate cells from tissues?
Use collagenase or microdissection. They can they be cultured in Petri dishes.
What are you the drawbacks of cultured cells?
They behave and look different to cells in tissues.
They demonstrate contact inhibition (when touch each other they stop growing).
Have a limited life span due to senescence.
What are the methods by which cells can die?
Necrosis and apoptosis
What is necrosis?
Caused by physical disruption to the cell by injury/bacterial toxins/nutritional deprivation. The cell loses functional control and osmotic pressure causes swelling in organelles, the chromatin clumps and the cell bursts. Cytotoxic cellular components spill out from the membrane and cause tissue damage and inflammation.
What is apoptosis?
Programmed cell death. Proteins inhibit and induce apoptosis. When apoptosis is induced catabolic processes begin throughout the cell. Enzymes digest cytostolic components and fragments of nuclear DNA. Capsases (protease) target proteins in nuclear laminar and cytoskeleton. Cell is repackaged for safe removal: chromatin condenses, cell shrinks and fragments into small apoptotic bodies. It is then phagocytised by adjoining cells.
What is endocytosis?
Bulk transport into the cell.
The cell membrane folds into a pouch surrounding the particles outside the cell. A vesicles is formed and carries the particles into the cell where they can be released.
What is phagocytosis?
A type of endocytosis. WBC engulf bacteria and unwanted cells and form a vesicle. This vesicle fuses with a lysosome which contains digestive enzymes which destroy the bacteria/unwanted cells.
What is exocytosis?
Bulk transport out of the cell.
A vesicle containing waste or cells products moves toward the cell membrane. The membrane around the vesicle fuses with the cell membrane. The contents of the vesicle are secreted as the membrane smooths out.
How often do cells in the body renew?
It depends. Some cells are static (CNS, cardiac and skeletal muscle cells)/stable (fibroblasts, endothelium, smooth muscle cells)/renewing (blood, skin epithelium, gut epithelium).
What are the two main types of organisms?
Prokaryotes and eukaryotes (endosymbiosis. mitochondrion/chloroplast engulfed by them).
What are the 4 basic types of tissues?
Epithelial
Muscle
Nerve
Connective
What are the different specialised connective tissues?
Adipose Lymphatic Blood Haemopoietic Cartilage Bone
What parts of the body are epithelium?
Covers exterior body surface
Lines internal closed cavities and body tubes that communicate with the exterior
Forms secretory portion of glands and lines their ducts
Specialised- receptors for special senses
What are the epithelial cell domains?
Apical domain- attach to nothin
Lateral domain- attach to each other
Basal domain- attache to basement membrane
Do epithelial cells exhibit polarity?
Yes
What specialisations can be on the apical domain?
Microvilli
Stereovilli
Cilia
What are microvilli?
Cytoplasmic processes that extend from the cell surface.
What are stereovilli
Particularly long microvilli e.g. In ear
What are cilia?
Motile cytoplasmic processes that beat in synchrony with a rapid forward movement (effective stroke) and a slower return movement (recovery stroke).
Why do necrotic cells swell and burst?
Failure of action of Na K ATPase (sodium potassium pump)
Which moves 3 Na+ out and 2 K+ in using ATP for energy
What is osmosis?
The net movement of water molecules from a high water potential to a low water potential through a selectively permeable membrane.
What is osmolarity?
Amount of solute/protein in water.
Concentration of a solution expressed as the number of solute particles per kg of solution. mOsm/kg
Usually 300mOsm/kg in plasma.
What is oncotic pressure?
Amount of protein in water
What is the electrical difference between the inside and outside of the cell membrane?
Membrane potential (-70mV)
Sodium and potassium in plasma vs. Intracellular
High sodium in plasma
High potassium in intracellular
What can happen if the stomach loses mucus?
Gastric ulceration and perforation.
What is pH?
pH= -log [H+]
What does a one unit change in the pH scale mean?
A ten fold change in the normal scale
What can cause abnormal plasma pH?
Major organ dysfunction e.g. Lungs/kidney/liver
Shock-poor tissue perfusion
What is shock?
A state of globally cellular and tissue hypoxia due to reduced oxygen delivery, usually due to hypoperfusion.
What are the types of shock?
Cardiogenic, hypovolaemic, septic shock
What happens when tissues are poorly perfused?
Anaerobic respiration leads to lactic acid production and lactic acidosis which impairs cardiac function.
What are the functions of connective tissue?
Connects cells to form tissues, tissues to form organs and organs to form the body. Can also provide support.
Transportation- provide a medium for diffusion of nutrients and wastes
Protection- provide a cushion between tissues and organs and provides insulation.
Storage (adipose tissue)
Defence against infection
Wound healing
What is the bulk of connective tissue made up of?
Extracellular material (matrix)
What are the 3 types of connective tissue?
CT proper e.g. loose/dense
Specialised CT e.g. blood/lymph
Supporting CT e.g. bone/cartilage/bone marrow
What is connective tissue made up of?
Ground substance
Fibres
Specialised Cells
(Cells make fibres and ground substance
Matrix=fibres and ground substance)
Does connective tissue or epithelial tissue have an abundant blood supply?
Connective tissue
What are the types of CT proper?
Loose and dense CT
What do loose and dense CT do?
Fill the space between organs and keep them in tact.
What is the most abundant type of CT?
Loose CT
What does loose CT contain?
Reticular, collagen and elastic fibres
Viscous Ground substance
Fixed cells e.g. fibroblast responsible for general maintenance of tissue
Wandering cells e.g. defence cells responsible for defending and repairing damaged tissue
Types of cells and what they do (loose CT)
Fixed:
Melanocytes-produce melanin
Macrophages-immune cells
Mast cells-stimulate local inflammation by releasing histamines
Fibroblasts-produce extracellular fibres
Adipocytes-store fatty reserves
Mesenchymal- stem cells responsible for repair of tissue
Wandering: Plasma cells Wandering macrophages Leucocytes Monocytes Eosinophils Basophils
What fibres are in loose CT?
Reticular
Collagen
Elastic
What do reticular fibres do?
They form branching networks which protect the organs.
What do collagen fibres do?
They provide resilience and strength
What do elastic fibres do?
They can recoil after stretching
What are the 3 types of loose CT?
Areolar
Adipose
Reticular
Where do you find areolar tissue?
Beneath all epithelial layers
What cell types does areolar tissue contain?
All cell types previously mentioned
What are the characteristics of adipose tissue and where is it found?
It has limited extracellular space and lots of adipocytes which form a cushion around delicate organs. Also found under skin for insulation and protection.
Which fibre dominates reticular CT and what does it do?
Reticular fibres dominate to form tough flexible scaffolds for delicate structures e.g. glands
How does dense CT differ from loose CT?
More fibres
Less ground substance
Fewer cells (fibroblast is main cell)
What are the 3 types of dense CT?
Dense regular- collagen fibres in parallel bundles
Dense irregular- collagen fibres in haphazard direction
Elastic- more elastic than collagen fibres