Midterm Exam Flashcards
What are the two types of intracellular substances?
Fibrous
Amorphous ground substance
What is the function of fibrous intracellular substances?
Strength and support - polypeptide chains
main type = collagen fibres
What are some morphological aspects of collagen fibres?
white in flesh state
form insoluble tannic acid after treatment with heavy metal - tanning which turns collagen to leathery sheet
three polypeptide chains of procollagen
aggregate to form 1-12 micrometer fibrils
What synthesizes and secretes collagen fibres?
fibroblasts chondrocytes osteoblasts epithelial basement membrane etc
Where are collagen fibres particularly abundant?
ECM, especially connective tissue
Why are collagen fibres so tough?
covalent H-bonds are formed between adjacent rows of molecules
What makes up the majority of tendons?
lined up bundles of collagen
what synthesizes and secrets reticular fibres?
Fibroblasts and other cells
What are some differences between reticular fibres and collagen fibres?
contain more sugar
do not bundle as much as type 1 collagen fibre
What are some morphological features of reticular fibres?
made of type 3 collagen with more sugars
stains with silver
typically 20 nanometer fibrils
stain with periodic acid-schiff (structure rich in sugar)
quite tough due to cross linking (similar to collagen)
What is the function of reticular fibres?
Supportive scaffolding, bridge transition to type 1 collagen
forms a net like support framework –> reticulum
What are the two main components of elastin fibres?
bundles of protein = elastin, rich in proline and glycine
Glycoproteins such as fibrillin which organizes into microfibrils
What are some morphological features of elastin fibres?
Yellow in fresh state
Sheets of fibres and networks
stain darker, thinner and more abundant than collagen which stain lighter and thicker
ribbons of microfibrils usually 1-4 micrometers
what binds ribbons of elastin fibrils covalently?
desmosine
What is the function of elastin fibres?
stretching and distension
Where are elastin fibres found?
Ligaments, larynx and some arteries
What is the purpose of the link between fibrils of elastin fibres?
allows fibrils to maintain their integrity during stretch and recoil
What secretes and synthesizes elastin fibres?
fibroblasts and smooth muscle cells
What are some morphological features of amorphous ground substance?
Viscous, clear, slippery
Viscosity varies with amount of cross linking
altering negative charge can also alter viscosity - lower neg charge in eye than bone in leg
What synthesizes and secretes amorphous ground substance?
fibroblasts
What are the components of amorphous ground substance?
Proteins, glycoproteins and carbs
glycosaminoglycans (GAGs) - repeating disaccharide units that are negatively charged and attract water (gel-like, major component)
proteoglycans - glycosaminoglycans attached to proteins
multi-adhesive glycoproteins - fibronectins and laminins which link to cell surface and regulate cell movement
hyaluronic acid - long, rigid, bound to proteins to form proteoglycan aggregates
what is the function of amorphous ground substance?
soft, fluid-like –> aids diffusion of tissue fluids
Firm gel-like –> resists more compression
Where are the different kinds of amorphous ground substances found?
Soft –> tissues, humours of the eye
Gel –> synovial fluid in joints, cartilage
Where is tissue fluid derived from?
Source = blood
hydrostatic pressure at arterial end of capillaries
What does tissue fluid consist of?
Water, salts, nutrients, hormones and oxygen
How is tissue fluid returned?
- Capillary absorption via osmosis and pinocytosis
2. lymphatic absorption - very permeable
What are the four primary tissues?
Epithelium - Cells closely apposed, little ground substance, sheets covering and lining surfaces
Connective tissue - Cells widely spread, variable amount of ECM, abundant collagen fibrils
Muscle tissue - elongated contractile cells, closely associated, skeletal and smooth
Nervous tissue - cells with elongated processes, specialized electrical impulses
What did the innovation of eumetazoa allow for?
Compartmentalization: New intracellular compartments
-coelenteron, mesoglea, excretion
physiological regulation and specialization:
- digestion, transport, of nutrients and gases, excretion
What innovation came before epithelium and how was it different from true epithelium?
Epitheloid (porifera and placazoa)
- relatively loose and not resting on anything (still close together)
How did epithelium evolve?
Cnidarians and ctenophora: cells rest on basal lamina of laminin and type 4 collagen
Bilateria: cells rest on basal lamina also in coelom and allows for a distinct circulation system
What are the basic morphological features of epithelium?
sheets of cells arranged in either single (simple) or multiple layers (stratified)
covers and lines surfaces and cavities
What is the function of epithelium?
Selective barrier - mechanical resistance
Secretory - enzymes, mucus and hormones
Absorption - facilitated diffusion, creates gradient
transport - pinocytosis/ exocytosis
sensory - specialized epithelium such as the retina
How is integrity of the epithelium maintained?
Laterally via intercellular bridges and junctions known as junctional complex of terminal bar
Basally via junctions to the basement membrane
What are the three kinds of junctions found in the intercellular bridges of epithelium?
- Tight occluding junctions ZO (zonula ocdudens)
- contain several transmembrane proteins
- establishes diffusion barrier to water
- establishes functional domains in plasma membrane - Anchoring junctions (ZA and MA)
- ZA: attach to actin via vinculin-actinin - removal of calcium leads to dissociation
- MA/desmosomes: attach to intermediate filaments by attachments plaques, mechanical stability and force dissipation by linking cytoskeleton of cells
- calcium trigger cadherin zipper binding - Gap junctions
- connexins: proteins that make up channels which line up and may react to messages to change their conformation (open/close)
- direct communication between cells –> ions, amino acids and metabolites
- coordinate activity between cells
What three layers make up the basement membrane of epithelium?
- lamina lucida: cell coat, protein linkers (integrin) between cytoskeleton and lamina densa
- lamina densa (basal lamina): cross linked proteoglycans, type four collagen and laminins
- Reticular lamina: network of reticular fibrils attached via anchoring fibril loops, type 3 collagen
What are the function of the basement membrane?
- Structural attachment between epithelium and ct
- anchored by hemidesmosomes and focal adhesions ( cell to ECM anchoring junctions) - Compartmentalization
- basal lamina separates epithelium and ct - Filtration
- Ionic charge in basal lamina plays a role in kidney ultrafiltration - neg charge allows certain molecules to pass - Regulation and signalling
- influencing epithelial cell shape, proliferation, differentiation, motility during development and regeneration - Tissue scaffolding
- Basal lamina guides new cells or processes during regeneration
What are the three(actually 4) types of epithelia?
- Squamous - Width greater than height
2, Cuboidal - Equal width, depth, height - Columnar - Height greater than width
- Pseudostratified epithelium(RARE) - nuclei at different levels, but all rest on basement membrane
What is endothelium and mesothelium?
Simple squamous: epithelia lining blood vessels and covering organs respectively
What is the function of stratified epithelia?
Protection against friction or shearing eg. skin epidermis
What are the four types of stratified epithelia?
Stratified squamous epithelium - superficial layer squamous
Stratified cuboidal - sup layer cuboidal
Stratified columnar - sup layer columnar
Transitional epithelium - sup layer changes w/ distension eg. urinary bladder
What is the difference between cilia and microvilli?
Both increase SA for exchange
Cilia are much larger
Cilia have microtubules inside that allow for motility
Microvilli have actin filaments for support, not motile
What are some examples of the earliest forms of CT?
Mesohyl of sponges
Mesoglea of cnidarians and ctenophores
Coelom walls of bacteria allowing for more specialization
What are the three main components of CT
Cells
Fibrous components
Amorphous intracellular ground substance
How and why is CT the primary tissue?
Morphology - separation between cells
Continuous compartment and distinct functions vs. other primary tissues
What are the prominent resident cells of CT?
Fibroblasts
Mast cells
Macrophages
Adipose cells (large, white)
What are the morphological features of fibroblasts?
Shape- fusiform, spindle shaped
Nucleus - oval/elongate, stain dark
Cytoplasm - homogeneous, weakly basophil (stain light)
What is the function of fibroblasts?
Synthesis of fibrous components and ground substance
What are the morphological features of mast cells?
Shape - irregular oval
Nucleus - Spherical but inconspicuous
Cytoplasm - large #of basophilic granules
Can clearly see nucleus and surrounding membrane
What is the function of mast cells?
Secrete granules containing the following mediators of inflammation in response to allergens
- hesparin
- histamine
- eosinophil and neutrophil chemotactic factors
What are the morphological features of macrophages?
Shape - ovoid (wondering) to stellate (fixed), shape is variable and depend on activity
Nucleus - kidney shaped
Cytoplasm - dark w/ small granules, lysosome present
What is the function of macrophages?
Phagocytosis and participate in immune response
“antigen-presenting cells”
Engulf foreign materials, bring them into cytoplasm and digest/ break into small parts that are trafficked to the membrane and signal communication to other cells and begin immune response
What are the morphological features of adipose cells?
Shape - spherical, ovoid
Nucleus - flattened against periphery
Cytoplasm - Thin layer around fat globule
What is the function of adipose cells?
Store lipids and release when needed, mechanical protection, temperature control, secrete hormones such as liptin which is involved in energy balance regulation
What are the transient cell populations of CT? *predominantly blood cells
Plasma cells * most abundant form of ct Lymphocytes Eosinophils Monocytes *these three are rare but abundant during acute inflammation
What are the morphological features of plasma cells?
Shape- ovoid
Nucleus - spherical and small
Cytoplasm - basophilic around golgi apparatus which indicates high metabolic activity in this region
What is the function of plasma cells?
Production of a specific antibody - must be activated
Types of connective tissue proper
Loose connective tissue
Dense connective tissue
*differentiated by proportions of cellular, fibrous and amorphous components
What are some general features of loose ct?
Glandular tissue is surrounded by white -> fewer bundles of collagen and purple nuclei
What are some examples of loose connective tissue?
Mesenchyme Mucoid ct areolar ct adipose tissue (white or brown) reticular tissue
What are the features and functions of mesenchyme?
fetal tissue, embryonic ct sparse collagen and fibroblasts cells are pluripotent Source for all connective ct loose and irregular
What are the features of mucoid ct and where is it found
embryonic ct found un umbilical cord
Contains: stellate fibroblasts, jelly-like mucous gland substance, mesenchymal stem cells
What are the features of areolar ct and where is it found?
Beneath epithelia and around small blood vessels
Contains: all major cell types, abundant ground substance, collagen and elastin fibres
What are the features of white vs. brown adipose cells?
White: unilocular or multilocular cells, reticular fibre network surrounding cells, sparse supply of capillaries
Brown: multilocular cells, sparse reticular fibres between cells, rich supply of capillaries, heat production function
What are the features of reticular tissue and where is it found?
Fine and loose supportive cells
made of type 3 collagen sometimes wrapped around by specialized reticular cells
found in the liver, spleen, lymph nodes, bone marrow and in adipose tissue
What is the function of dense ct and how is it able to perform this function?
Resist stretching and provide strength
Proportionately large amount of fibrous elements
What are the different kinds of dense ct, where are they found and what are their features?
dense irregular ct: abundant collagen fibres arranged in irregular directions, found in the capsule of organs and the dermis (strength to skin)
dense regular ct: collagen fibres are regularly arranged, found in tendons, ligaments and cornea
What is the difference between the ECM of cartilage vs. bone?
ECM of cartilage has highly charged proteoglycan aggregates making it hard and pliable - much more flexible than in bone
ECM of bone is calcified via CaPO4 which makes it hard and rigid
How does cartilage develop?
develops from mesenchyme that condenses to form cartilage and initial skeletal structure –> the chondrogenic nodule
Most becomes ossified and replaced by bone
mesenchyme cells differentiate into chondroblasts which secrete cartilage matrix and becomes enclosed in small cavities called lacunae
Chondroblasts become chondrocytes which divide and produce more ground substance and fibres
