Lecture 11 - Musculoskeletal System 1: Bones Flashcards
What % of body mass does bone material make up
Roughly 20%
How many bones are in humans body
206
The skeletal system consists of: (4)
- bones
- cartilage
- joints and articulations
- ligaments
What are 6 functions of bone
- Support
- Movement
- Protection
- Storage: Growth factors & Minerals
- Storage of energy
- Hematopoiesis
How does bone provide support
Long bone and antigravity muscles
How does bone provide movement
Acts as a lever for muscle action
How does bone provide protection (examples)
Bones of cranium protect brain, vertebrae protect spinal cord, ribs protect lungs etc
What are the growth factor and minerals stored in bones
Calcium and phosphate, which are essential for nervous and muscle systems
What energy source do bones store and in what part of bone
They store lipids in the yellow bone marrow
What are the types of bone tissue
Compact and cancellous (spongy)
What are the 4 types of bones
Long, short, flat, irregular
What is the structure of long bone
- longer than wide
- 1 diaphysis, epiphysis
- mostly compact, with some spongy in epiphysis
- role of support
- only type of bone that has medullary cavity
Where are some Long bones
Arm, forearm, palm, finger, thigh, leg, sole, toes
What is the structure of short bone
- small, almost cubic
- filled with spongy bone, covered by thin layer of compact bone
Where might you find short bone
Wrist (carpals), ankles (tarsals)
What is the structure of flat bones
- Thin, flat, slightly curved
- Filled with spongy bones (diploe), covered by a thick layer of compact bone
- Protection role, large surface for muscle attachment
Where would you find flat bones
Cranium, sternum, ribs, scapula
What is the structure of irregular bone
- Complex forms and composition varies
- Spongy bone, fine layer of compact bone
Where would you find irregular bone
Vertebrae, bones of face, coxal bones
What are Sutural bones
They are special irregular bones that are between sutures of cranial bones (ex. lambdoid suture at back of head)
What are sesamoid bones
-Small round bone imbedded in a tendon to help reinforce and decrease stress on that tendon
Where are sesamoid bones
In the knee / Patella but also in some ppls hands and feet
What is diaphysis
- Body of a long bone
- Thick cylinder of compact bone with medullary cavity filled with yellow bone marrow
What is epiphysis
- End of a long bone
- Filled with spongy bone and covered by thin layer of compact bone
- The part that takes part in articulation is covered in articular cartilage (hyaline)
What is epiphysals line
- Remnant of epiphyseal cartilage where growth takes place up until end of adolescence (metaphysis)
What is periosteum
- Membrane that covers the bone (lacks cartilage)
- Contains cells important for repair and growth
What are 2 layers of periosteum
- Fibrous: external, dense irregular CT, neurofibers, blood and lymphatic vessels
- Osteogenic: internal, osteoblasts & osteoclasts
What is endosteum
A membrane that cover:
- Medullary cavity
- Trabeculae
- Canals that cross compact bone
- Osteoblast and osteoclasts
What is the diploe sandwiched in between in flat bone
An upper and lower layer of compact bone which is covered in periosteum imagine: periosteum compact diploe compact periosteum
What are 2 components of Bone matrix and %
- Organic 35%
- inorganic 65%
What are the organic specialized cells that make up bone matrix
- osteoblasts (create the matrix)
- osteoclasts (removes deposited mineral)
- Osteocytes (bone forming cells)
What are the organic Osteoid (ground substance) that make up bone matrix
- proteoglycans, glycoproteins, chondroitin sulfate, collagen fibers (secreted by osteoblasts)
- leading to flexibility, resistance to pressure and adhesion
What is the makeup of inorganic materials that make up bone matrix (%)?
- 10% calcium carbonate
- 5% other minerals (Mg+, Na, SO42-, F-)
- 85% hydroxyapatites (crystals of calcium)
Function of inorganic materials in bone matrix
-The salts (hydroxyapatites) are deposited in, on and btw collagen fibers like cement around its brace, to give it hardness, solidity and rigidity
what % of bone is compact
80%
Where is compact bone
Forms external layer of bone surface and most of diaphysis
what is function of compact bone
Support, protection
what is functional unit of compact bone
Osteon
-it is made up of 6-15 lamella/ layers (haversian system)
What increases compact bone solidity
Collagen fibers alternate orientation in each layer
What runs through central canal (Haversian) and in what direction
Blood, lymphatic vessels and nerves parallel with length of long bone
What runs through perforating canal (Volkmann) and in what direction
Blood, lymphatic vessels and nerves and the run perpendicular off central canals and into spongy bone
What is between each lamella (layer) of compact bone
A lacuna that contains an osteocyte
What do the osteocytes in the lacuna do
Communicate with exterior via canaliculi and btw themselves through projections
-they exchange nutrients via gap junctions
What is in between Osteons (osteon = Haversian canals 6-15 lamella (layers) of collagen fibers in circle pattern)
interstitial lamella which are remnants of old osteons
-they have osteocytes and canaliculi but are not connected to central canals
What % of bone is spongy bone
20%
Do spongy bones have osteons?
no
What forms the trabeculae
Elongated or flattened osteocytes between irregular lamellae made lattice like structure = trabeculae
What dictates orientation of the trabeculae
According to the constraints that bone is subjected to and is not haphazard
- develops to be strongest and most shock absorbent it can
where do osteocytes in trabeculae of spongy bone get nutrients and blood
from blood that circulates between trabeculae interlinked via the canaliculi
what is in the spaces between trabeculae
Red bone marrow (RBM)
Where is there red bone marrow
exclusive to long bone epiphysis, hip, rib, thoracic cage, vertebrae, cranium
What are osteogenic cells
- from mesenchyme (stem cells)
- can divide and become osteoblasts
What are osteoblasts
- They lose capacity to divide when they transform into osteocytes
- secrete collagen and osteoids
What are osteoids
- proteoglycanes
- glycoproteins
- collagen fibers
What are osteocytes
- Osteoblast that eventually get covered in matrix and lay down within lacunae
- they do not secrete matrix
- maintain bone tissue and exchange things like waste and nutrients with blood and other cells
What are osteoclasts
- Large multi-nucleated cells
- they are macrophages found at surface of bone and they destroy the matrix
- they are essential as they guarantee renewal, growth and repair
Bone marrow distribution in newborns
There is very little in the epiphysis of long bone
- most in medullary cavity of long bone
- only red bone marrow
Bone marrow distribution in adults
Main bone still contain red bone marrow but some is replaced by yellow mallow
What can happen if excess calcium in blood
- cardiac contraction
- propagation of nerve impulses
What is homeostasis of calcium 4
- Calcium circulation is very closely regulated
- Calcium is important to many enzymes and blood coagulation
- Bone serves as a calcium reserve ( release and absorb as needed)
- Important hormones act on calcium
What are the 2 important hormones acting on calcium for homeostasis
Parathyroid hormone (PTH) Calcitonin
What is parathyroid hormone
Hormone released from chief cells of the parathyroid gland when calcium is low
What does PTH do
- Stimulates activities and reproduction of osteoclasts
- increases kidney absorption of calcium from urine
- if there is an increase in vitamin D it increases absorption of calcium from intestines
Where does Calcitonin come from
Secreted by paraflocular cells of the thyroid
What does Calcitonin do
- Released when calcium concentration is high
- inhibits osteoclast activities
- stimulates calcium deposition by osteoblasts
What is ossification
The process of bone formation
Why does bone grown in width during a lifetime
- For remodeling
2. consolidation of bones, making them stronger
When do bones stop growing
Never, it is a continuous process throughout life
What is the skeleton formed of at 6th week of gestation
- Fibrous membranes
2. Hyaline cartilage
What are 2 types of ossification processes that occur at 8 weeks of gestation
- Intramembranous ossification
2. Endochondral ossification
What is intramembranous ossification
- From fibrous membranes
- Give rise to intramembranous bone
- Most of the cranial bones, clavicles, and flat bones
What is endochondral ossification
- From hyaline cartilage models
- Give rise to endochondral bone
- Majority of the skeletal bones
What is the formation of a ossification center in intramembranous ossification
- The inside of the fibrous CT membrane
- Mesenchymal cell aggregate and differentiate into osteoblasts
What is the secretion of the matrix in intramembranous ossification
- osteoblasts secrete the osteoid that is calcified in a few days
- osteoblasts become trapped in the lacunae and will become osteocytes
What is the formation of spongy bone in intramembranous ossification
- osteoid is deposited btw embryonic blood vessels
- forms network of trabeculae that trap the blood vessels
What is the formation of periosteum in intramembranous ossification
- Mesenchymal cells join the surface of the bone and differentiate into layers:
1. External layer
2. Internal layer - osteogenic cells
What is formation of compact bone in intramembranous ossification
-Compact bone (external)and osteogenic layer of the periosteum (internal)
Why is endochondral ossification a complex process
Because hyaline cartilage must be broken down as the bone ossification process proceeds
The modeling of Hyaline cartilage primary center ossification
- Primary center ossification
- perichondrium is penetrated by blood vessels that transform it into the periosteum
The modeling of Hyaline cartilage formation of a bone collar
- Formation of bone collar around the diaphysis
- mesenchymal cells of the periosteum differentiate into osteoblasts that secrete a cylinder of osteoid
The modeling of Hyaline cartilage: calcification of the cartilage in the center of the diaphysis and formation of the bone cavity
- chondrocytes expand & burst, which modifies PH levels
- Calcification of the matrix
- when calcified, there are no nutrient exchange
- chondrocytes die
- Matrix disintegrates
- Bone cavity is formed
The modeling of Hyaline cartilage: penetration of the cavities by the periosteal bud and formation of the spongy bone
-New osteoblasts secrete osteoid on the cartilage fragment which form the trabeculae of spongy bone
The periosteal bud contains
The periosteal bud contains nutrient artery and vein, lymphatic connections, neurofibers, red bone marrow elements, osteoblasts, osteoclasts
The modeling of Hyaline cartilage: formation of medullary cavity and the initiation of secondary ossification centers in the epiphysis
- process of enlarging and shedding of ossification center
- Osteoclasts break down the new spongy bone which forms the medullary cavity (center of the diaphysis)
The modeling of Hyaline cartilage: ossification of the epiphysis occurs before or right after birth
These are 2nd ossification center in the epiphysis and happens similar to diaphysis process
Process of ossification of epiphysis
Cartilage calcifies - matrix breaks down - obtain cavity - periosteal bud enters matrix or cavity - new osteoblasts secrete osteoid - create trabeculae with spongy bone
Distinction between formation of diaphysis and epiphysis
Epiphysis has no bone collar or medullary cavity
Final product of ossification of epiphysis
- articular cartilage at the surface of the epiphysis
- epiphyseal plate cartilage (the junction between the epiphysis and diaphysis)
What is the first formed bone called and what does it develop into
Called woven bone and develops into lamellar bone
What are primary osteons replaced by
They are demineralized areas around blood vessel, they grow from out to in; and are eventually replaced by secondary osteons
Why is bone remodeling important
For homeostasis, let’s bone grow in size and shape
what is in constant flux after bone growth complete
Ossification and reabsorption (but total size does not change)
Where does bone gain and loss occur
Gain from outer surface, loss from within
what remodels trabeculae
Mechanical stress remodels it to better withstand stress
-higher stress = narrower tube for new osteon
When is ossification faster and when is reabsorption faster
Youth has more ossification
after 40 more reabsorption
Bone mass is influenced by:
Stress
-muscle tension, gravity
Stress on bone mass stimulates
- bone regeneration
- narrowing of osteons
- calcitonin (inhibit bone reabsorption)
- ossification
People who have low bone mass:
- live in weightlessness for long times
- Are bedridden
What does intense exercise cause to bones
Reinforcement of bones
Bones of the arm
Scapula humerus radius (thumb) ulna(elbow) olecranon (the elbow joint)
Rib bones
7 true ribs
3 to 5 false ribs
floating ribs
total = 12 to 14 ribs
Bones of sternum
Manubrium (connects to clavicle)
Body
Xiphoid process (bottom of sternum)
Parts of spine
- intervertebral disk
- body(where bulk force goes)
- transverse process
- spinous process
Where are the atlas and axis in spinal column
Cervical spine c1 and c2
Bones of pelvic girdle
- sacrum
- coccyx
- illium
- ischium
- pubic symphysis
- acetabulum
Bones of the hand
- metacarpals (in palm_
- carpals (8 bones in wrist)
- phalanges (fingers)
Bones of wrist / carpals
- trapezium
- trapezoid
- scaphoid
- hamate
- capitate
- pisiform
- triquetrum
- lunate
What are 3 parts of phalanges
- distal
- middle
- proximal
What are 3 parts of metacarpals and what’s the 1st metacarpal
-head
-shaft
-base
1st is thumb
bones of legs
- pelvis
- hip joint
- femur
- patella
- fibula
- tibia
Bones of foot
- talus (accepts weight from tib/fib)
- calcaneus (heel)
- tarsal
- metatarsals
- digits/ phalanges
name the tarsals (5)
Cuboid Navicular Medial cuneiform Lateral cuneiform intermediate cuneiform
what is first metatasal in foot
big toe
parts of toe digits
- proximal phalanx
- middle phalanx
- distal phalanx
