Session 7: Bone marrow, vessels and blood Flashcards
Name the bones of the axial and appendicular skeletons
Axial: Skull, vertebra, thoracic cage(ribcage)
Appendicular: shoulder girdle, pelvic girdle, lower and upper limbs
Explain how a bone is a living tissue
Bones have their own blood vessels, and proteins, minerals which allow them to grow, transform and repair themselves through life
What is the function of bones?
- Protects important and delicate tissues and organs
- Haemopoiesis: holds and protects bone marrow
- Fat storage( yellow BM), acid-base homeostasis absorbs or releases alkaline salts-has Ca, to regulate blood pH)
How are bones formed?
- Endochondral ossification: formation of long bones inside cartiliage. Continued lengthening throughout life by ossification of growth plate- called appositional growth growth at edges)
- Intra-membrous ossification: formation of bones from clusters of mesenchymal(MSC) bone marrow cells from centre of bone. Called intersitial growth- growth begins in middle
How do bones undergo remodelling?
- Bone resorption: osteoclasts digest old bone
- Ossification: bone formed by osteoblasts lay down new bone till resorbed bone is completely replaced
Describe the components of bones( in a fetal skull)
Osteoblasts: bone deposition
Osteocytes: osteoid recycling
Osteoclasts: bone resorption
Periosteum: blood supply for bones( side 1)
Mesenchymal tissue: in bone marrow, make and repair skeletal tissue
Spicule of bone: fragments of bone marrow, connect to form tracbaculae
Osteoid: unmineralised bone tissue
Lacunae: contains osteocyte left behind by osteoblast after remodelling
Canaliculi: links lacunae with one another and with haversian canal. Also found in liver lobule
Lamellae: extracellular matrix around cells that gives compact bones it hardness.
Endosteum: lining membrane of bone marrow cavity, lines haversian canal( side 2)
Trabacular bone: porous bone connected with thin rods and plates
Haversian and Volkmann’s canals: carry blood vessels, lymph vessels and nerves
Describe the structure of cancellous/trabecular/spongy bone and compact/cortical bone which make up every bone in the body
Cancellous: network of fine bony platse called trabeculae to combine strength with lightness. Spaces are filled with bone marrow
Compact: forms externla surfaces of named bones, contains Ca
Explain the importance of Vitamin D in normal bone stability
Vitamin D produces calcitrol which aids in calcium absorption
How does activity of osteocytes affect bone stability?
- Activity of osteocytes( osteoid recycling): can act like osteoblasts and lay down scavenged osteoid into lacunae due to increased oestrogen or thyrois hormones OR can act like osteoclasts and degrade bone, called osteocyctic osteolysis( increased by PTH/parathormone, secreted by parathyroid gland which controls Ca levels in blood)
How does activity of osteoblasts affect bone stability?
Bone deposition is stimulated by oestrogen, testosterone, thyroid hormones, vit A
How does activity of osteoclasts affect bone stability?
Bone resorption is increased by PTH, releases calcium ions into blood. To counteract, calcitonin decreases Ca levels by blocking PTH at PTH receptor.
What biological change generally causes bone disease?
Depletion of bone mass. Loss of mass within trabecular bone is relevant to increased suspectibility to fracture.
Describe the genetic and phenotypical changes in osteogenesis imperfecta
AKA brittle bone disease. Caused due to autosomal dominant mutations in COL1A where produced mutated collagen 1 fibres do not knit together or insufficient collagen is produced. Results in:
weakened bones, short stature, blue sclera, hearing loss, loose joints, flat feet, crowded teeth
Describe the features of bones affected by rickets and phenotypical changes, and compare with osteomalacia
R: mainly in children, due to Vit D deficiency. Leads to poor calcium mobilisation, weak bones, short stature, painful walk, characteristic bowed legs
O: rickets in adults, Vit D def, increased osteoid-unmineralised bone tissue, bones are weak. Leads to increased calcium resorption. Due to lack of sunlight, Ca rich food, esp when preganant. Fetus needs Ca for own tissue development as well.
Describe the radiological and structural changes in primary and secondary osteoporosis
Primary
Type 1: post menopausal women due to increase in osteoclast number, loss of osetrogen in menopause- osteocyte cannot act as osteoblast anymore
Type 2: older people due to loss of osteoblast function AKA senile osteoporosis and loss of oestrogen and androgen. Incomplete filling of osteoclast resorption bay.
Secondary
Due to drugs like corticosteroids( asthma treatment), affects bone remodelling. OR due to malnutrition, space travel, lack of movement OR metabolic bone disease
What are some modifiable risk factors for osteoporosis?
- Insufficient calcium intake: recommended value for postmenopausal women is 700mg/day
- Exercise: immobilisation of bone leads to accelarate bone loss, exercise needed to maintain bone mass.
- Cigarette smoking: in women, smoking is correlated with increased incidence of osteoporosis
Outline the causes and features of achondroplasia
Causes: inherited mutation in the FGF3 receptor gene
FGF( fibroblast growth factor) promotes collagen formation from cartilage( endochrondrial ossification affected, intramembrane ossification not affected)
Features: short stature, but normal sized head and torso AKA dwarfism as long bones cannot lengthen properly
Describe characteristic features and functions of long bones
Longer than they are wider. Eg: femur, and small bones in fingers. Mostly located in apprendicular skeleton.
Function: support weight of body and facilitate movement
Require cartiilage, develop through endochondral inside cartilalge) ossification.
Describe characteristic features and functions of short bones
Approximately as long as they are wide. Eg: carpals in wrists and tarsals in ankle joints
Function: provide stability and movement
Describe characteristic features and functions of flat bones
Somewhat flattened, roughly parallel opposite edges. Eg: skull( occipital lobe), thoracic cage(ribs and sternum), pelvis.
Function: protect internal organs, provide large areas of attachment for muscles
Develops directly from mesenchymal tissue through intra membrane ossification
Describe characteristic features and functions of irregular bones
Vary in shape and structure, but usually have complex shape.
Function: Vertebrae protect spinal cord, pelvis protects organs in pelvic cavity, provides important anchor points
Describe characteristic features and functions of sesamoid bones
Embedded in tendons. Small, round bones in tendons of hand, feet, knees. Eg: patella( near knee cap), generated post natally
Function: protect tendon from stress and damage from repeat wear and tear
What are the constituents of the bone marrow?
Hematopoietic cells: myeloid( creates RBC, monocytes, granulocytes and platelets) and lymphoid( creates T cells, B cells, natural killer and innate lymphoid cells)
Marrow adipose tissue: red and white
Supportive stromal cells: connective tissue
What are the constituents of the blood?
Platelets
Plasma
Blood cells
State the structure and function of bone marrow
semi-solid tissue found within spongy or cancellous portions of bones, produces new RBC. Stem cells can be used to treat illnesses
What are the different kinds of blood cells? State their structure and function
- Erythrocytes: no nucleus, biconcave disk, flexible-can pass through small vessels. Includse small proportion of recticulocytes, new RBC has nuc, cannot transport O2. Function- O2 transport from lungs and CO2 back. Endothelial cells in kidney sense low O2, increase erythropoietin, RBC production increase, no more hypoxia
- Leucocytes:
(A)granulocytes( lobed nucleus, cytoplasm with granules) and (B)mononuclear cells( normal nucleus, no granules in cytoplasm)
(A)
Neutrophils: pale cytoplasm, actually lysosomes with digestive enzymes. Function- phagocytosis at site of infection, process called chemotaxis. Occurs in response to other white cells singnalling. GColonySFactor increase neutrophil production, chemotaxis.
Eosinophils: bi lobed nucleus, cytoplasm with orange granules that stain red. Ingest antigen-antibody complexes, in high levels in allergic conditions like asthma, hay fever etc.
Basophils:granules stain blue or purple. Released into tissue at injury site- vasodilation and oedema due to hitamine and histamine prevents clotting. Both parts of basophils.
(B)
Monocytes: irregularly shaped nucleus, contains lysosomes. Becomes macrophages and phagocytise like in kupffer cells in liver. Return to circulation after infection subsides through lymphatic system.
Lymphocytes: Nuclear much bigger than cytoplasm, involved in immune response to foreign materials. Contain 75% T cells that recognise antigens and kill their host cells. Also stimulate transformation of B cells into immunoblasts.
What are the different kinds of platelets? State their structure and function
Cytoplasm contains alpha and dense granules.
Alpha granules: contain fibrinogen
Dense granules: contain ADP and calcium
Platelets assist in clotting. Activates prothrombin into thrombin, soluble fibrinogen to insoluble fibrin to form clot.
Describe the structure and function of blood vessels from arteries to veins
Look at table in notes
Explain the functional significance of communicating/ collateral blood vessels
Provide alternative path for arterial blood flow, due to tumours in arteries or blockages, or durign development. Provides protection for compormised tissues
What is the difference between vasculogenesis and angiogenesis
Vasculo: formation of new blood vessels from bone marrow
eg: newly formed cancers
Angio: formation of new blood vessels from existing vessels. eg: collateral arteries
Explain 2 possible routes of formation of vasculogenesis during embryogenesis
First step: production of a single vessel
Sprouting: Angiogenesis
Perictyes convert into smooth muscle cells- slow, takes hours to days, like branching off pre existing vessels
Division of primary vessel: Intussuspection
Splitting one vessel into 2, explains why arteries and veins are close together in neurovascular bundles. Quick, takes mins to hours
Name major blood vessels of body and determine whether they are oygenated/ deoxygenated
Look at notes
What are 2 connective tissue layers the bone is surrounded by?
Periosteum: outside
Endosteum: inside
Both vascular
White vs red bone marrow
Red:
Full of developing cells, rich blood supply, only found in spongy bone. Function- haemopoiesis
Yellow: full of adipocytes, poor blood supply. Function- shock absorber and energy source, can convert to red marrow during blood loss
Difference between immature and mature bones
Immature: osteocytes in random arrangments
Mature: osteocytes in concentric lamallae of osteons
