[B] (Pt 1) Human Musculoskeletal Anatomy: SKELETAL TISSUES Flashcards
Germ Layers (x3)
Early embryonic pluripotent stem cells arranged in germ layers (cells will become all tissues body)
i.e. endoderm (inner), mesoderm, ectoderm (outer)
Connective Tissue
- Connects + supports organs/ other tissues
- Cells embedded in matrix w collagen fibres + elastic tissue
- Develops from mesoderm
e.g. cartilage/ bone
Cartilage
Hard, flexible connective tissue in respiratory airways + end of bones + anterior end ribs + nose + outer ear
1) Hyaline Cartilage
2) White Fibrous Cartilage (fibrocartilage)
3) Yellow Elastic Cartilage
Chondrocytes
Cells in cartilage:
- Secrete an extra-cellular matrix made of transparent protein chondroitin (may contain fibres collagen/ elastic material)
- In spaces in matrix (lacunae)
Properties Cartilage
- Rigid: hold open tube e.g. trachea/ Eustachian tube
- Flexible: allows ribcage movement
- Returns original shape after bending: role load bearing joints e.g. hips/ knees
(No blood vessels: nutrient acquisition/ gas exchange rely diffusion - diffusion slow so healing slow)
(No nerves)
Hyaline Cartilage
Weakest
Role: Prevents friction at joints
- High proportion collagen (in extra-cellular matrix)
- “Glassy”
- Surrounded fibrous coat connective tissue (perichondrium)
- If damaged replaced fibrocartilage scar tissue
- Ossifies in foetus (becomes bone) + in adults is articular cartilage at ends of bones
e. g. joining ribs w sternum/ nose/ larynx/ trachea/ bronchi
White Fibrous Cartilage (fibrocartilage)
Strongest
Role: Load bearing in intervertebral discs
- Collagen organised in dense fibres (higher tensile strength) + in direction of stress
- Makes intervertebral discs + ligaments
Yellow Elastic Cartilage
Intermediate Strength
Role: Maintains shape at epiglottis
- Chondrocytes surrounded collagen (in matrix) + network elastin fibres
(makes it elastic but maintains shape)
e.g. ear pinna/ epiglottis
Bone: Functions (x4)
- Structural support skeleton
- Movement (bones attachment sites for muscles)
- Physical protection organs e.g. brain
- Mineral regulation: storage (e.g. Ca/P), trapping harmful mineral (e.g. lead), regulation calcium content
Bone: Types (x2)
1) Spongy/ Cancellous Bone
2) Compact Bone
Spongy/ Cancellous Bone
Found end of long bones + in vertebrae
Light + porous and has network of spaces containing bone marrow (flexible tissue where RBCs made)
Compact Bone
Strong and rigid + surrounds most bones - gives white/shiny appearance (75% bone body)
Haversian + Volkmann canals run through bone so blood vessels can penetrate
OSTEOBLASTS: Continuously build it up
OSTEOCLASTS: Continuously degrade it
–> cells held in matrix secreted osteoblasts (30% organic collagen fibres to resist fracture + 70% inorganic hydroxy-apatite (mineral rich Ca and P) v hard and resists compression)
Haversian System/ Osteon
- Structural and functional unit of compact bone
- Separated by interstitial bone
- Formed concentric lamellae (rings made hydroxy-apatite secreted by osteoblasts in lacunae) around central Haversian canal
Periosteum > interstitial bone > lamellae > Haversian Canal > marrow cavity
(+ lacunae + Volkmann canals + Canaliculi)
Haversian Canal
- Centre of Haversian System
- Contains an arteriole, a venule, lymph vessels and nerve fibres
Volkmann Canal
[Haversian System]
Perforating canal that connects Haversian canals with each other and with the periosteum (carries blood vessels)
Canaliculi
[Haversian System]
Microscopic channels that radiate out of lacunae (containing osteoblasts) into bone matrix
–> forms 3D network between osteoblasts to supply nutrients via blood vessels + remove waste (also some exchange by diffusion through bone matrix)
Bone Formation: Cartilage Bones
e.g. limb bones/ vertebrae/ ribs
OSSIFICATION of hyaline cartilage in embryo:
(begins ends/ middle long limb bones)
- Cartilage cells flatten + Ca deposited around them
- Osteoblasts secrete layers bone matrix around cartilage while osteoclasts break down cartilage
- Blood vessels invade
Perichondrium surrounding cartilage –> periosteum surrounding bone (dense fibrous connective tissue)
Bone Formation: Membrane Bones
e.g. collarbone (clavicle)/ most skull (cranium)/ facial bones
–> form directly in embryonic connective tissue
Bone Diseases (x3)
1) Rickets + Osteomalacia
2) Brittle Bone Disease (osteogenesis imperfecta)
3) Osteoporosis
Rickets + Osteomalacia
Rickets: Childhood disease where Ca not absorbed into growing bones so become soft/ weak/ deformed
Osteomalacia: Milder rickets in adults
Symptoms: Tenderness/ fractures/ bone deformity e.g. bow legs toddlers/ knock knees/ less wide pelvic girth women (difficulty childbirth)
Diagnosis: Blood tests (low Ca)/ x-rays/ bone density scans
Cause: Lack vitamin D/ Ca (sunlight converts inactive to active vitamin D which incorporates Ca into bones)
Prevention: Exposure sunlight + Ca in diet + vit D (fat soluble so found butter/eggs/fish)
Treatment: Vitamin D/Ca supplements/ ultraviolet B light exposure/ surgery for bone deformities
Brittle Bone Disease [osteogenesis imperfecta (OI)]
Inherited disorder in balance organic vs inorganic components bone - leading increase risk fractures
Symptoms: Fractures/ poor muscle tone/ loose joints
Diagnosis: Test collagen from skin biopsy/ DNA analysis
(Normally collagen has high proportion smallest amino acid glycine but OI replace w bigger amino acids so cannot coil tightly so H-bonds holding triple helix weaker - interaction triple helix w hydroxy-apatite altered so brittle bones)
Cause: Genetic (mutations in type 1 collagen)
Treatment: No cure
- Drugs (increase bone mass, reduce pain/ fractures)
- Surgery (metal rods in long bones to walk)
- Physiotherapy (strengthen muscles, mobility)
Osteoporosis
Abnormal loss of bone mass + density due Ca leached from bones resulting increased risk fracture
Symptoms: Fractures arm, wrist, hip, vertebrae/ stooped posture/ chronic back pain
Diagnosis: Bone scan measure mineral density in hip
Causes/ Risk Factors:
- Age (post-menopausal women rapid loss bone density due drop oestrogen/ old men due drop testosterone)
- Lack Ca in diet
- Family history
- Inflammatory conditions e.g. rheumatoid arthritis
- Medical conditions/ drugs that affect hormone lvls
- Alcohol/ smoking
Prevention/ Treatment: No cure
- Diet rich Ca/ vit D
- Regular load bearing exercises (increase bone density)
- Drugs (increase Ca uptake in bones)
- Give up smoking/ less alcohol
- Prevent falls
Types of Muscle (x3)
- Skeletal (striped, striated, voluntary)
- Non skeletal (unstriped, non striated, smooth, involuntary)
- Cardiac
Skeletal Muscle: Structure of Muscle Tissue
(Muscle fibres = long thin cells)
Fascicle = Bundle of muscle fibres
(Surrounded by connective tissue - perimysium)
Muscle = Bundle of fascicles
(Surrounded by connective tissue - epimysium)