BONE + BLOOD Flashcards
(24 cards)
the entire skeleton is renewed ~ 10 yrs, name three factors that modulate physiological bone formation, loss and remodelling
- hormones
- parathyroid
- vit D metabolites
- calcitonin
- GH - mineral metabolism
- calcium + phosphate - functional - mechanical factors
- disuse atrophy
name the THREE histological types of bone
- haversian [lamellar] bone
- woven [fibrous] bone
- bundle [sharpey’s fibre] bone
bone is the ____ form of ____of which ____ % is ____, which is a similar size to that of ____
the crystals are found in around type ____ collagen
by volume the greatest proportion of bone is ____
the vitality of bone + ability to continuously form, modify or respond to injury is dependent on
1.
2.
bone = calcified form of collagenous CT, of which 60% of the weight is made up by hydroxyapatite crystals - of a similar size to those found in dentin/cementum
the apatite crystals are found in/around the type 1 collagen
by volume the greatest proportion of bone = collagen
vitality and ability to form, modify and responsd to injury is dependent on the presence of
1. bone stromal tx [bone marrow]
2. bone cells [osteoclasts/blasts/cytes + periosteum]
describe haversian [lamellar] bone
- makes up normal adult skeleton
- all cortical + cancellous bone is this type
structure
- multiple, tightly packed, repeating, concentrically layered bone units [osteon circle in middle + rings around it]
- osteon pattern [aka haversian bone] - each osteon unit is based on vascular supply is haversian canals of bone
- osteocytes = concentrically arranged in lacunar within osteon, along junction of adjacent lamellae + parallel to outer cortical bone surface
outline what resting/reversal lines are and what they indicate
- darker stained lines in decalcified sections of bone
- indicators of bone activity/remodelling
resting lines
- smooth contour = reflecting periodic cessation of bone matrix formation
reversal lines
- scalloped contour reflecting Howship’s lacunae pattern of previous bone resoption and subsequent new bone formation
describe woven bone
occur in situations eg emryogenesis, bone healing, neo-plastic bone diseases, tumours
embryonic woven bone is replaced by haversian bone with age
structure
- irregularly shaped trabeculae of condensed collagen matrix [lacks osteon/lamellae structure of lamellar bone]
if
woven bone = being actively formed = trabeculae will be lined w plump osteoblasts [forms matrix]
if bone = quiescent phase = devoid of matrix lining cells
describe bundle bone
- found on outer cortical surface of bone at tendon site + musc insertions
- also lines tooth socket
- characterised by sharpey’s fibre which contributes the connection between ligaments + bone
differentiate between osteocytes, osteoblasts and osteoclasts
osteocytes
- mature bone cells
osteoblasts
- responsible for prod collagen + ground substance = forms bone matrix
- found lining surface of cortex + trabeculae, separated from min. matrix by thin osteoid zone [unmin. matrix before]
may be in/active
active = lined w plump OB cells w prominent cytoplasm, lining osteoid during matrix prod then integrates w bone matrix forming osteocytes
inactive = flattened OB cells w elongated nuclei that line osteiod
also recruit OC when resoprtion needed
osteoclasts
- derived from monocytes, recruited by molecular signalling [eg by OB] when resorption needed
- multinucleate cells
- as they resorb matrix = prod. shallow, scalloped depression [Howship’s lacunae] - seen in reversal lines
when activated
1. remove bone first by releasing proteins = dissolve apatite crystals
2. then prod. enzymes which remove organic matrix
evidence of Howship’s lacunae in histological bone sections is indicative of
previous bone remodelling and OC resorption
describe the TWO methods of bone formation
- intramembranous ossification
- begins as framework of woven bone = later replaced by haversian bone
eg most skull bones, flat bones of face, collarbone - endochondral ossification
- begins as framework of hyaline cartilage in shape of particular bone –> then replaced by bone during embryogenesis/later growth
eg long bones [leg/arm], hands, feet, base of skull
describe cartilage, where its found, its composition and its THREE types
- specialised form of CT [tough, resilient, flexible, can cope w stress]
- forms major part of embryonic skeleton
- resp. for long bone growth [leg/arm] + some mandible growth at TMJ condoyle
found
- forms primary mandible
- ends of long bones
- joins ribs-sternum
pubic symphysis
- TMJ
- nose, ear
- intervertebral discs
composition
- ECM [collagen, PGs, GAGs, GPs, can contain elastin]
- matrix
water 70-75%
collagen 15-20% [TS]
PGs 2-10 % [resilience]
types
1. hyaline
2. elastic
3. fibrocartilage
describe hyaline cartilage, where its found, functions and structure
- most common + best studied
found
- articular ends of long bones
- epiphyseal plate [growth plate of long bones]
- ends of ribs [joins them –> sternum]
- trachea, bronchi, larynx, nose
func
1. cushioning
2. allows smooth joint articulation
3. bone formation at ends of long bones
4. formation of organs/tx rq strenth but flex. eg trachea, larynx
structure
- surrounded by periochondrium [except at articulating ends of long bones] = dense fibrous CT containing fibroblasts, BV, peri.nerves, lymphatics [also + undiff mesenchymal cells that –> chondroblasts which form chondorocytes
- avascular [receives supply via diffusion through ECM from periochondrium
- articular hyaline cartilage receives supply from synovial fluid in joint spaces
ECM
- water 70-75%
- collagen 15-20% [type 2, 9,10,11]
- PGs 2-10%
- GAGs + GPs
describe interstitial growth and appositional growth of hyaline hartilage
interstitial
- growth through division of existing chondorcytes = more ECM
- occ mainly in immature devel + imp. in epiphyseal plate enlargement
- also the mechanism for repair following damage
- responsible for lengthwise growth of bones
appositional
- NEW chondrocytes arise in periochondrium from mesenchymal cells = form new ECM matrix on existing cartilage surface
- mech. of growth for most hyaline cartilage [except articular hyaline
- responsible for diameter growth of bones
describe elastic cartilage, where its found and functions
hyaline cartilage + elastic fibres [also has perichondrium]
found
- external ear [auricle]
- walls of external auditory canal
- part of larynx
- epiglottis
func
- maintains shape
- allows flex.
describe fibrocartilage, where its found and irs functions
mix of v dense collagenous fibrous [type 1 collagen] + areas of cartiliage cells + small amts of cartilage matrix
found
- pubic symphysis
- intevertebral disc
- discs of knee joints
- parts of ligaments
- articular surface of TMJ condoyle
- articulating tx of TMJ =contains hyaline but referred to as fibrocartilage bcos it contains BOTH type 1 + 2 collagen
func
- attachment of bony parts
- cushioing
- TS [resists pulling]
describe the composition of blood + FIVE functions
comp
1. plasma
2. RBC
3. WBC
4. platelets
[approx 55% plasma 45% RBC, 1% platelets, 1% WBCs]
males = 12 pints
females = 9 pints
func
1. transport O2 + nutrients –> lung/tx
2. blood clots to prevent excess blood loss
3. carrying cells + ABs that fight infection
4. bring waste products –> kidneys/liver for filtering
5. reg. body temp
describe the composition and origin of plasma
- water
- proteins eg albumin, ABs
- dissolved salts/ions
- nutrients
- hormones
- cell + tx waste product
- gases
origin
- prod in liver via reticuloendotherial cells
then other components added
serum = blood plasma which is STRIPPED of cells, albumin, clotting proteins
list 8 cell types of blood + where RBCs are prod from
- erythrocytes [RBC]
- platelets
- leukocytes [WBC]
- monocytes
- lymphocytes
- neutrophils
- eosinophils
- basophils
RBCs = prod from stem cells in haemopoeitic [red] bone marrow via haemopoeisis/lymphopoeisis
erythrocytes have a ____ % blood cell count, are ____ microns in diameter and have a lifespan of ____
their func is to ____
~44% blood cell count
8 microns diameter
lifespan of ~ 120 days
func = transport O2 using Hb and CO2
defiencieny in RBCs = anemia
platelets are ____ microns in diameter, have a lifespan of ____ and derive from _____
their primary role is ____
~ 2 microns diamter
lifespan of 4-7 days
derive from megakaryocytes in bone marrow + anuclear
primary role = blood clotting
describe macrophages, and FOUR functions
- bone marrow derived
- exist in blood as monocytes and in tx as macrophages
- give rise to diff type of multinucleate cells eg OC
func
1. phagocytosis
2. immune surveillance
3. antigen processing
4. cell recruitment
differentiate polymorphonuclear neutrophils, eosinophils and basophils
neutrophils
- most commonly assoc w acute inflammation + prinicpal role in PHAGOCYTOSIS
- short lived - first line of defence - cannot return to circulation
- contain large # membrane bound granules which aid phagocytosis
eosinophils
- found in circ + tx
- contain granules [large = small]
- capable of phagocytosis but func is mostly to release granules
- for defence against helminthic infections + rol in acute/chronic inflammation, hypersensitivity reactions
basophils
- SMALLEST of PMN leukocytes
- assoc mostly w mast cells in type 1 hypersensitivity reactions
- poorly understood detailed features
describe lymphocytes
- catergorised as
1. T-lymphocytes - cell mediated immunity and T cell immune memory
- long life span [can enter/leave/re-enter circ]
- recognise antigens by APCs
TWO TYPES
1. t-helper cells [CD4+]
- form 60% of mature T cells
- activation through exposure to cell bound antigen + MCH2 complex on APCs
t1 helper cells
- sec. IL-2 and INF-y + involved in inflam. proc. an macrophage activation, and killer T cells
t2 helper cells
- sec IL-4 + IL-5 + primary func = activating B cells to form AB prod plasma cells
- t-suppressor cells [CD8+]
- form ~ 30% mature T cells where most develop –> cytotoxic killer killer cells - B-lymphocytes
- AB mediated immunity and B cell memory
