Skeletal System
Monday, October 10, 2022
Functions of skeletal system:
Shape & form (support)
Movement (muscles use bones as levers)
Protections by encasing organs fully or partially
Mineral storage of calcium and phosphate, lots of minerals
Blood cell formation/hematopoiesis occurs in some bones
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Classification of bones:
Axial skeleton: straight line of the skeleton, vertebral column
- Skull, Vertebrae, Ribs
Appendicular skeleton: appendages
Limbs, Shoulders, Hips
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Unique shape of each bone fulfills a particular need/function
Bones are also classified by shape
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Long bones:
- Longer than they are wide
- Has a shaft and two ends
- Bones = clavicle/collarbone, limbs, fingers (except patella, wrist, and ankle)
Short bones:
- Cube shaped
- Sesamoid: bone formed in tendon (patella/kneecap, pisiform)
- Bones = wrist (carpels) and ankles (tarsals)
Flat bones:
- Thin, flattened
- May be curved
- Bones = sternum, scapula, ribs and most skull bone
Irregular bones:
Complicated shape
Bones = vertebrae, sacrum, mandible, hyoid, coccyx, most facial bones, and hip bones(ilium, ischium, pubis)
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Skeletal cartilages:
Human skeleton is initially made of cartilage
Most cartilage is replaced by bone
Cartilage remains in areas where flexibility is needed
Cartilage
- Avascular (no blood cells)
- No nerves
Chondrocytes: cells that make up cartilage
Typical growth ends during adolescence (skeleton stops growing)
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Types of cartilage:
Hyaline: most common; in the skeleton, these cartilages include …
- Articular(where ever the 2 bones meet)
- Costal (rib cage)
- Respiratory (voice box)
- Nasal (front of the nose)
Elastic: found only in external ear and in epiglottis; most flexible
Fibrocartilage: occur at sites of high pressure (knee, between vertebrae, etc)
Tuesday, October 11, 2022
Joints:
Any site where 2+ bones meet
Main functions:
Help us move
Hold skeleton together
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Type of Joint | Fibrous(tough) | Cartilaginous(bendy) | Synovial(slidey) |
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Term for Movement (SAD) | Synarthroses | Amphiarthrosis (amphibian can be on water and land, cartilaginous can be movable and immovable) | Diarthroses |
Amount of Movement | Immovable | Slightly moveable | Freely moveable |
Additional info. | Bones joined by fibrous tissue | Articulating bones are united by cartilage | All joints of limbs fall into this class |
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Fibrous joints:
Sutures: between skull bones; interlocking joints; keeps bone together; stops movement
Syndesmosis: bones connected by ligaments; mainly for supporting movement
Gomphosis: peg in socket; only found in the tooth and gum; through the root of the tooth
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Cartilaginous joints:
- Synchondrosis: chondro = cartilage; bar/plate of hyaline cartilage; unites bones
- Symphysis: surface of bones covered with fibrocartilage
Synovial joints:
- Plane
- Flat articular surfaces; slides on top of one another(front, back, side to side); allow slipping or gliding movements; (notebook on table; planes in math)
- Ex: vertebrae, thumb carpals
- Hinge
- Opens and closes, uniaxial joints (permits flexion and extension)
- Ex: elbow, phalanges
- Pivot
- One bone locked in place and another bone can move around that bone; rounded bone end protrudes into sleeve of bone or ligament
- Ex: atlas and axis(head rotation), radius and ulna(forearm rotation)
- Condyloid
- Oval surface fits into depression; convex and concave; biaxial(permit angular motions); like swings- front to back, side to side, swing
- Ex: radiocarpal; metacarpophalangeal; bottom finger joint to the hand
- Saddle
- Each articular surface has a concave and convex surface; biaxial
- Ex: thumb only
- Ball-and-socket
- Being able to make full circles; spherical head articulates with a cuplike socket; multiaxial(permit most freely moving)
- Ex: shoulder, hip
Thursday, October 13, 2022
Bone structure:
Bones contain: nervous tissue, cartilage, fibrous connective tissue, muscle, epithelial tissue
- Bones contain various different tissue: this makes them organs
Bone is made of:
Compact bone: dense outer layer
Spongy bone: internal layer; pattern in which spongy bone is layered is trabeculae: small honeycomb of needle-like bone
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Long bone
- Diaphysis (shaft)
- Long axis of bone; thick collar of compact bone; surrounds marrow cavity
- In adults: yellow bone marrow cavity = contains fat (yellow marrow)
- Epiphysis (bone end)
- Exterior = compact bone; Interior = spongy bone
- Joint surface covered with a articular cartilage
- In adults: epiphyseal line = between diaphysis and epiphysis; remnant of growth plate
Short, flat, and irregular bones
- No marrow cavity, no shaft, no epiphysis
- Ribs, skull, etc
- Contain red bone marrow between trabeculae
- Flat bones: spongy bone = diploe (stiff sandwich of compact - spongy - compact)
Tuesday, October 18, 2022
Long bone:
Periosteum:
- Externa; surface of entire bone (except joint surfaces) rich with nerve fibers, lymph vessel, and blood vessels
- Outer layer = dense irregular connective tissue
- Inner layer = osteoblasts and osteoclasts
- Anchoring point for tendons and ligaments
- Sharpey’s fibers: secures periosteum to the underlying bone by perforating bone
Short, flat, and irregular: thin plates covering compact bone
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Endosteum:
- Delicate connective tissue that covers trabeculae of spongy bone
- Lines canals of compact bone
- Contains osteoblasts and osteoclasts
Short, flat, and irregular: covering spongy bone
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Bone cells:
Osteocytes: maintains bone tissue; are the bone tissue
Osteoblasts: forms bone matrix; start of the bone
Osteogenic cells: stem cells; can change into any other type of bone cell
Osteoclasts: resorbs bones; breakdown the bone to allow new cells to form there
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Hematopoiesis:
- Production of blood cells
- Long bones: occurs in the head of femur and humerus; closest to the point of attachment so red blood cells are created closer to the trunk where it is needed more
- Flat & irregular: red marrow of diploe is much more active; occurs in sternum, hip, and more
- Yellow marrow can revert to red marrow if red blood cell production is needed
Wednesday, October 19, 2022
Osteons (haversian system): Structural unit of compact bone; group of hollow tubes placed one inside the other; tubes inside of tubes inside of tubes next to tubes inside of tubes
Elongated cylinder: lamella (compact bone - lamellar bone)
Oriented parallel to long axis of the bone
Tiny weight bearing pillars
Central canal (haversian canal): runs through core of each osteon; contains nerves and blood vessels
Volkmann’s canal: right angle to bone axis; connect blood/nerve of the periosteum to central canals and marrow cavity
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Osteocytes:
Spider shaped mature bone cells
Filling the whole between the plates
Occupy lacunae at lamellar junctions
Canaliculi: hair like canals; connect lacunar to each other and central canal
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Trabeculae:
Align along the lines of stress; help bone resist stress
No osteons are present
Contains irregularly arranged lamellae
Osteocytes interconnected by canaliculi
Nutrients reach spongy bone by diffusion through capillaries in endosteum
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Ossification /osteogenesis: osteo = bones; genesis = formation
- Babies have zero bone when in the womb, it's all cartilage
- Conversion of cartilage to bone; bones start at cartilage
- Bone growth until early adulthood
- Bones altar in thickness, remodeling, and repair
Ossification process:
Osteoblasts appear in cartilage
Osteoblasts secrete osteoid and osteocytes get trapped in bone
Blood vessels weaving into the bone and the periosteum forms
Lamellar bone is developed/formed and osteocytes, osteoblasts, and osteoclasts are all present; keeps happening until your bones are fully formed
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Bone growth:
- Infancy /youth: long bones get longer; all bones grow in thickness;
- Adolescence: most bones stop growing; females stop growing at around 18; males stop growing at around 21
- Adult: ossification mostly remodeling
Monday, October 24, 2022
Bone growth - hormones:
Growth hormone: released by pituitary gland; makes you bones grown in length and thickness
Thyroid hormone: regulates activity of the growth hormone; ensure proper proportions for growth
Adolescence/puberty: sex hormones promote growth spurt; later, hormones end longitudinal bone growth
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Bone remodeling:
Regulated by:
- Blood calcium levels (Ca2+) negative feedback
- Hormones: PTH (parathyroid hormone) & Calcitonin
- Response to forces (mechanical or gravitational) on skeleton
Purpose: repair skeleton damage, prevent accumulation of old bone, obtainstore calcium & phosphorus
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Occurs when: bone is injured, bone strength needed
For optimal bone deposit, you need: a lot of things
- Proteins, vitamin C, D, A, minerals(calcium, phosphorus), blood, nerves, etc.
Wolff’s law:
- Bone grows or remodels in response to the demands placed on it
- For example…
- Featureless bones of fetus
- Atrophied bones of bedridden people
- Thickened bones of weight lifters
Friday, October 28, 2022
Scoliosis:
- “Twisted” disease
- Abnormal lateral curvature of the thoracic vertebrae
- Idiopathic (without a known cause)
- Treatment: physical therapy to strengthen muscles; rod down vertebrae
Lordosis:
- Abnormal curvature of lumbar vertebrae
- “Sway back”
- Idiopathic
- Treatment: usually fixes itself (in children); may require physical therapy
Kyphosis:
Exaggerated posterior curvature of thoracic vertebrae
“Hunchback”
Treatment: medication(for pain); surgery
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Imbalance:
Osteomalacia: soft bone disease; calcium is not deposited; lack of vitamin D;
- Rickets: osteomalacia in kids; mostly in children; bowed legs and other bone deformities
Osteoporosis: bone resorption outpaces bone deposit; decreases bone mass; calcium deficiency
- Risk factors: decline in estrogen levels, petite body form, poor diet/exercise, smoking, age
Ostealgia: bone pain; caused by arthritis or fracture
Osteogenic sarcoma: bone cancer; affects osteoblasts; occurs most often in the bones of teenagers during growth spurt; treatment: chemotherapy
Osteonecrosis: bone death; loss of blood supply to a bone; caused by crushed bones or diabetes; pain, limitation of motion, muscle/joint spasm in area
Osteoarthritis: more common; cartilage wears down with movement; primary effect on weight bearing joints(knees, hips, back, nack, shoulder); maintain movement
Rheumatoid arthritis: immune system attacks own joints/body; come with other symptoms (fever, loss of appetite, weight loss); primary effect on smaller joints; limited movement