L3 - Connective Flashcards
Types of fibres
Collagen, reticular, elastic
Proteoglycan formation
GAGS + core protein
Sulphated GAGS
Dermatan sulphate, keratan sulphate, chondroitin sulphate, heparin sulphate
Non-sulphated GAGS
Hyaluronic acid
CT function
- binds, supports, strengthens other body tissues
- protects, insulates internal organs
- main source of immune responses
- compartmentalise structures (e.g skeletal muscles)
- major transport system of body (blood)
- major site of stored energy reserves (fat/adipose tissue)
CT features
- NOT found on body surfaces
- can be highly vascular
- supplied with nerves
CT blood vessel/nerve supply exception
Cartilage: avascular, no nerves
Tendons: very little blood supply
ECM structure examples
Fluid, semifluid, gelatinous, calcified
CT qualities
- Affected by ECM structure
- how tissue develops, migrates, proliferates (multiplies), changes shape and how metabolic functions are carried out
ECM composition
- ground substance
- protein fibres (secreted by cells in ECM)
Ground substance function
- support cells
- bind cells together
- provides medium for exchange of substances between blood and cells
- stores water
Ground substance composition
Water, proteins, polysaccharides
Fibronectin
Adhesion protein that links ground substance to collagen fibres and cell surfaces
GAGS structure
- long unbranched polysaccharides
Repeating disaccharide unit of amino sugar and uronic sugar
GAGS features
- highly polar and attract water thus traps water to make ground substance more jelly-like
Types of GAGS
Sulphated, non-sulphated
Sulphated GAG function
Bind to proteins to form proteoglycans
Dermatan sulphate location
Skin, tendons, blood vessels, heart valves
Keratan sulphate locations
Bone, cartilage, cornea of eye
Chondroitin sulphate locations
Support/provide adhesive features of cartilage, bone, skin, blood vessels
Non-sulphated GAGs function
(Hyaluronic acid) doesn’t directly bind to protein backbone but is joined to various proteoglycans
Hyaluronic acid features
- not sulphated nor covalently bound to core protein
- viscous slippery substance
Hyaluronic acid function
- binds cells together
- lubricates joints
- maintain shape of eyeball
Hyaluronidase production
By leukocytes, sperm and some bacteria that want to get through ECM
Hyaluronidase function
Makes ground substance more liquid by destroying hyaluronic acid so the producers can move more easily in it or make egg easier for sperm to access
Exopthalmos cause
- autoimmune action on fibroblasts in ECM of eye
- deposition of GAGs and influx of water increases orbital contents
Exopthalmos appearance
Eyeball protrudes forward due to reduced space at the back of eye
Exopthalmos features
Most common in young women
Goitre cause
Autoimmune over-activation of thyroid
Collagen fibre composition
Collagen protein (25% of proteins - most abundant)
Collagen fibres features
- thick, very strong but flexible (not stiff)
- often occur in parallel bundles (adds tensile strength)
- varies in different tissues
Collagen fibres function
- resist pulling forces (tension)
- provide strength and support
Collagen fibres location
Common in bone, cartilages, tendons and ligaments
Reticular fibres composition
Collagen in fine bundles with coating of glycoprotein
Glycoprotein
More protein than sugar/carbohydrate
Proteoglycan
More sugar/carbohydrate than protein - 55~95% GAG
Reticular fibres features
- thinner than collagen
- branching spreads through tissue
- made by fibroblasts
Reticular fibres function
- provide strength and support
- forms part of basement membrane
Reticular fibres location
Forms networks in vessels and through tissues especially areolar/adipose tissues, nerve fibres, smooth muscle
Elastic fibres composition
Elastin protein surrounded by glycoprotein, fibrillin, to give more strength/stability (contributes to a structural scaffold for elastin)
Elastic fibres features
- fibrous network branch/join together
- strong
- can be stretched 150% without breaking
- can return to original shape
- thinner than collagen fibres (thinnest)
Elastic fibres location
Skin, blood vessel walls, lung tissue
Marfan syndrome cause
- hereditary defect in elastic fibres usually resulting from a dominant mutation in a gene on chromosome 15 that codes for fibrillin
- body produces Transforming Growth Factor beta (TGFb) which doesn’t stay inactive due to not binding to fibrillin normally and thus increases growth
Marfan syndrome outcome
- tall, long limbs, chest deformity (protruding/collapsed sternum), normal life span but need medical vigilance to control BP
- may have weakened heart valves and arterial walls (life-threatening)
Marfan syndrome frequency
1 in 200,000 live births
Immature -blast cells
Retain capacity for cell division
Mature -cyte cells
Reduced capacities for cell division/ECM formation as mostly for monitoring and maintaining ECM
Fibroblasts location
- widely distributed in CT
- migratory (e.g across wound)
Fibroblast function
Secrete components of matrix (fibres and ground substances)
Adipocytes location
Under skin, around organs
Adipocytes function
Stores fat (triglycerides)
Macrophage appearance
Irregular shape with short branching projections
Macrophage features
- Fixed and wandering forms
- developed from monocytes (leukocyte)
Macrophage function
Phagocytic cells - engulfs bacteria/cellular debris by phagocytosis
Macrophage location
- fixed: dust cells (lung), kupffer cells (liver), Langerhan’s cells (skin), splenic (spleen)
- wandering: sites of infection/inflammation/injury
Plasma cells features
Developed from B-lymphocyte
Plasma cells function
Immune response: produce antibodies
Antibodies
Proteins that attack/neutralise foreign substances
Plasma cells location
Many CT sites but especially in gastrointestinal tracts (gut), respiratory tracts (lung), salivary glands, lymph nodes, spleen, red bone marrow
Mast cells function
- Inflammatory response: produce histamine that dilates vessels
- bind to, ingest and kill bacteria
Inflammatory response
Reaction to injury/infection
Mast cells location
Alongside blood vessels
Leukocytes location
Migrate out from blood
CT classification
Embryonic, mature
Embryonic CT
Mesenchyme, mucous
Mesenchyme structure
Consists of irregularly shaped mesenchymal cells (CT cells) in a semi-fluid ground substance containing delicate reticular fibres
Mesenchyme function
Gives rise to all other CT
Mesenchyme location
Under skin, developing bones of embryos, along blood vessels of adult CT
Mucous structure
- widely scattered fibroblasts embedded in jelly-like ground substance
- less cells
- contains fine collagen fibres
Mucous function
Supports
Mucous location
Umbilical cord of foetus
CT proper types
Loose, dense
Loose CT types
Areolar, adipose, reticular
Areolar structure
Consists of fibres (collagen, reticular, elastic) arranged randomly in cells (fibroblasts, macrophages, plasma cells, adipocytes, mast cells, few leukocytes) embedded in semi-fluid ground substance
Areolar function
Strength, elasticity, support
Areolar location
Widely distributed around almost every structure
Adipose structure
- adipocytes dominant
- central triglyceride droplet pushes cytoplasm/nucleus to cell peripheries
Adipose feature
Increases with weight gain + new blood vessels form
Adipose types
White adipose, brown adipose
White adipose function
Energy storage
Brown adipose function
Heat production
Brown adipose features
Very rich blood supply + numerous pigmented mitochondria that participate in aerobic respiration
Adipose function
Insulation (reduce heat loss through skin), energy source, temperature control (generate heat), supports/protects organs
Adipose location
- found in association with areolar CT
- Buttocks, flanks (side of body), abdomen, orbit of eye, subcutaneous layer deep to skin, around heart/kidneys, yellow bone marrow, padding around joints, and behind eyeball in eye socket
Reticular loose CT structure
Fine interlacing network of reticular fibres and reticular cells
Reticular loose CT function
- forms stroma of many soft organs (spleen, lymph nodes)
- binds smooth muscle tissue cells
- filters/removes worn-out blood cells in spleen and microbes in lymph nodes
Reticular loose CT location
Stroma of liver, spleen, lymph nodes, red bone marrow, reticular laminate of basement membrane, around blood vessels/muscles
Stroma
Supporting framework
Loose CT composition
More cells, fewer fibres
Dense CT composition
More fibres, fewer cells
Dense CT types
Regular, irregular, elastic
Regular. structure
- regularly arranged collagen fibre bundles with fibroblasts in rows between them
- shiny white coloured ECM
Regular. Function
- strong attachment
- withstand pulling (tension) along long axis of fibres
- slow healing: collagen fibres are not living tissues and not many cells are there to produce material needed to heal scar
Regular. Location
Tendons (pulling along fibre axis), ligaments, aponeuroses
Irregular. Structure
Made of collagen fibres usually arrange irregularly with few fibroblasts (making it dense)
Irregular. Function
Provides tensile (pulling) strength in many directions
Irregular. Location
Often in sheets such as fascsiae (tissue beneath skin/around muscles and other organs), reticular (deeper) region of dermis, fibrous pericardium of heart, periosteum of bone, perichondrium of cartilage, joint capsules, membrane capsules around various organs (kidneys, liver, testes, lymph nodes), heart valves
Elastic dense CT structure
- Contains predominantly elastic fibres with fibroblasts between
- unstained tissue is yellowish
- strong
Elastic dense CT function
- allows stretching of various organs
- can recoil original shape after being stretched
Elastic dense CT location
Lung tissue (recoil in exhaling), walls of elastic arteries (recoil between heartbeats to help maintain blood flow), trachea, bronchial tubes, true vocal cords, suspensions ligaments of penis, some ligaments between vertebrae
Mature CT types
CT proper, supporting CT, fluid CT
Supporting CT types
Cartilage, bone
Cartilage composition
Few cells, lots of ECM
Cartilage structure
- chondrocytes, lacunae, perichondrium, dense network of collagen (strength) and elastic fibres embedded in chondroitin sulphate ground substance (resilience)
Perichondrium
Covering of dense irregular connective tissue surrounds surfaces of most cartilage
- contains blood vessels/nerves thus source of new cartilage cells
Cartilage function
- resist tension (stretching), compression (squeezing), shear (pushing in opposite directions)
- can endure considerably more stress than loose and dense connective tissue (CT proper)
Cartilage location
Precursor to bone (forms entire embryonic skeleton), growth plates, lubricated articulate surfaces of most joints
Cartilage types
Hyaline, fibro, elastic
Hyaline structure
- relatively weak
- resilient gel (bluish-white, shiny substance) in which fibres are present but not obvious
- chondrocytes in lacunae surrounded by perichondrium (except articular cartilage in joints and cartilage of epiphyseal/growth plates)
Hyaline function
Flexibility, smooth surfaces for movement at joints, support
Hyaline location
- most abundant in body
- anterior ends of ribs, respiratory cartilage (nose, trachea, bronchi, parts of larynx, nasal septum), ends of long bones, embryonic/foetal skeleton
Fibro structure
- chondrocytes among clearly visible thick bundles of collagen fibres within ECM
- lacks perichondrium
Fibro function
- support and join structures together
- strength and rigidity make it strongest type of cartilage
Fibro location
Pubic symphysis (where hip bones join anteriorly), intervertebral discs, menisci (cartilage pads) of knee, portions of tendons that insert into cartilage
Elastic cartilage structure
- chondrocytes in threadlike network of elastic fibres within ECM
- perichondrium present
Elastic cartilage function
Provides strength and elasticity, maintains shape of certain structures
Elastic cartilage location
Epiglottis (lid on larynx), part of external ear (auricle), auditory (eustachian) tubes
Cartilage growth types
Interstitial growth, appositional growth
Interstitial growth when
Childhood/adolescence when cartilage is young/pliable
Interstitial growth how
Division of existing chondrocytes = more ECM from chondrocytes = matrix becomes more dense within lacunae = chondrocytes spread apart = cartilage rapidly expands from within
Appositional (exogenous) growth when
Starts later than interstitial growth + continues through adolescence
Appositional growth how
Inner cellular layer of chondrocytes differentiate into chondroblasts which secrete matrix (ECM) = chondroblasts surround in ECM and become chondrocytes = matrix accumulates beneath perichondrium and growth on outer surface of tissue
Bone composition
- several CT types including bone tissue, periosteum, red/yellow bone marrow, endosteum
- have mineralised/hardened ECM
Bone types
Spongy (cancellous), compact (cortical)
Spongy structure
- Porous inner bone tissue that lies underneath compact bone
- lacks osteons: instead have thin columns called trabeculae (components of osteons except central canal) where spaces between trabeculae are filled with bone marrow
Spongy function
Stores triglycerides (yellow marrow), produces blood cells (red marrow)
Compact structure
- outer layer of bone and forms shaft of long bones
- composed of many rod-shaped units called osteons/Haversian systems
Osteon composition
Lamellae, lacunae, canaliculi, central (Haversian) canal
Lamellae
Concentric rings of ECM containing mineral salts (calcium phosphate, calcium hydroxide - together form hydroxyapatite) for hardness, compressive strength and collagen fibres for tensile strength
Lacunae
Small spaces between lamellae that contain osteocytes
Canaliculi
‘Minute canals’ (containing EC fluid and minute osteocytic processes) that radiate from lacunae and provide routes for oxygen, nutrients and waste
Central canal
Contains blood/lymph vessels and nerves
Compact. Function
- stores calcium/phosphorus
- protect, support
- serves as levers that act with muscle tissue to enable movement
Bone cell types
Osteogenic, osteblasts, osteocytes, osteoclasts
Osteogenic cells
Mesenchymal stem cells that develop
- starts to lay down collagen then become trapped then become osteoblasts
Osteoblast cells
- bone-forming cells
- lay down more collagen
- mineralization process starts
Osteocyte cells
- mature bone cells derived from osteoblasts trapped within ECM
- maintain bone tissue
- involved in exchange of nutrients/wastes
- have gap junctions (connected to canaliculi)
Osteoclast cells
- large, multi-nucleated cells
- formed from fusion of blood monocytes (leukocytes)
- break down bone to access stores of calcium/phosphate and remodel bone if damaged
Fractures
- osteoclast: reabsorb dead bone
- chondroblast: lay down hyaline cartilage callus
- osteoblast: lay down new bone
- osteoclast: remodel new bone
Fluid CT types
Blood, lymph
Blood composition
Blood plasma, formed elements
Blood plasma (ECM)
Pale yellow fluid consisting of mostly water with dissolved substances (nutrients, waste, enzymes, plasma proteins, hormones, respiratory gases, ions)
Formed elements composition
Erythrocytes, leukocytes, platelets
Erythrocyte function
Transport oxygen and carbon dioxide
Leukocyte function
Combat disease
Leukocyte types
- neutrophils + monocytes (macrophages)
- basophils + mast cells
- eosinophils
- lymphocytes
Neutrophils + monocytes (macrophage) function
- phagocytic: engulf bacteria
Basophils + mast cells function
Release substances (histamine) that intensify inflammatory reactions
- basophils: mobile
- immature mast cells: circulate
- mature mast cells: fixed in tissues
Eosinophils function
Effective against certain parasitic worms and acute allergic responses
Lymphocytes function
Involved in immune response
Platelets function
- from megakaryocytes in red marrow
- blood clotting
Blood location
Within blood vessels (arteries, arterials, capillaries, venules, veins) and within chambers of heart
Lymph composition
- several cells in clear liquid ECM similar to blood plasma but with less protein
- composition varies between different parts of body
Protein fibre features
- secreted by cells in ECM
- different types present in different proportions
Osteon location
Aligned along lines of stress
E.g long axis of bone shaft
Cells in connective tissue
Most common: fibroblasts, adipocytes
Others (in combination with fibroblasts and adipocytes): macrophages, plasma cells, mast cells, leukocytes
Specialised CT
Fluid and supporting CT
Amino sugar example
N acetylglucosamine
Uronic sugar example
Glucuronic acid
