Skeletal
Osseous tissue is made of what type of tissue?
Connective
Functions of bones
Support, protection, movement, electrolyte balance, acid-base balance, and blood formation.
outer covering consisting of fibrous CT and a layer of bone-forming cells, attaches to cartilage.
Periosteum
Dense layer of osseous tissue that makes up the outer portion of a bone.
Compact bone
porous bone often found at ends of long bones and within flat bones. Always surrounded by compact bone
spongy bone
inner compartment that contains bone marrow
Marrow cavity
soft tissue composed of adipose tissue (YELLOW MARROW) and/or RED MARROW (HEMATOPOIETIC TISSUE that is responsible for blood cell formation). Red marrow decreases with age
Bone marrow
Yellow marrow tissue
adipose
Red marrow tissue
Hematopoietic
thin layer of reticular CT that lines the marrow cavity. Also contains OSTEOGENIC cells
endosteum
main shaft of a bone where many muscles attach
Diaphysis
end of a bone that articulates with other bones to form a joint
Epiphysis
layer of hyaline cartilage that separates the epiphysis from the diaphysis. In children and adolescents, this is the zone of dividing cells that allows bones to grow longer (a.k.a, “growth plate”).
Epiphyseal plate or line
Perforating holes that allow blood vessels to enter the bone and transport nutrients and waste
Nutrient Foramina
Since bone is connective tissue, it contains
cells, fiber, ground substance
undifferentiated cells that will mature and become osteoblasts. Found in endosteum and periosteum
Osteogenic cells
undifferentiated cells that will mature and become osteoblasts. Found in endosteum and periosteum
Osteoblasts
These are “retired” osteoblasts that live in LACUNAE
Communicate via GAP JUNCTIONS
Can “sense” mechanical stress
Small ability to deposit or resorb bone
Osteocytes
large multi-nucleated cells whose job is to dissolve bone. Similar origin as macrophages (blood derived)
Osteoclasts
non-cellular, ground substance of osseous tissue
bone matrix
Bone cell types
Osteogenetic cells, osteoblasts, osteocytes, osteoclasts
Bone matrix is made of
Organic protein matter and inorganic matter
Organic protein matter is mainly made of
collagen
organic protein matter makes up ___ of the bone matrix
1/3
inorganic matter makes up ___ of the bone matrix
2/3
Inorganic matter of the bone matrix is made of
Hydroxyapatite and calcium carbonate
2 or more structural componants are called
a composite
inorganic matter gives bones
strength and rigidity
organic matter gives bones
flexibility
brittle bones
osteogenesis
too soft
osteomalcia or rickets
central canal surrounded by circular layers of bone matrix
Osteon
circular layers of bone matrix surrounding a central canal
lamellae
runs the length of a bone and contain blood vessels and nerves
Haversian canal
cavities which contain osteocytes
Lacunae
tiny ducts between lacunae and allow osteocytes to communicate via gap junctions
Canaliculi
allows communication between central canals and/or nutrient foramina
Volkman’s Canal
a meshwork of thin rods and plates of osseous tissue (TRABECULAE)
spongy bone
Types of bone marrow
Red and yellow
Red marrow is found in what parts of the body?
pelvis, skull, ribs, heads of femur and humerus
Red bone marrow does what with age?
disappears
Yellow bone marrow is found in
Adipose tissue
Red marrow turns into
yellow marrow
Red bone marrow function
blood formation
Red marrow is what type of tissue?
Hematopoietic
Where the lacunae of the cartilage grow larger and become calcified (hardened)
Primary ossification center
Blood vessels enter the primary ossification center, then
osteoblasts convert hyaline cartilage to osseous tissue, chondrocytes proliferate
convert hyaline cartilage to osseous tissue
osteoblasts
secondary ossification centers
blood vessels invade the epiphyses of the bone creating
secondary ossification centers eventually hollow out into
secondary marrow cavities
secondary marrow cavities fill with
spongy bone
Epiphyseal Plate is between
primary and secondary marrow cavities
this is on the surface of the ends of you bones
articular cartilage
How does bone grow with endochondrial ossification?
Length
Bone elongation steps:
Chondrocytes of the hyaline cartilage in the epiphyseal plate grow larger and multiply
As cartilage layer expands, the cartilage at the upper and lower edges of the epiphyseal plate becomes ossified
Process of expansion/ossification at the metaphysis repeats over and over, thereby extending the length of the bon
Growing pains are
the epiphyseal plate expanding faster than the periosteum muscle covering
Hyaline Cartilage is precursor to
osseous bone tissue
The widening and thickening of bone is called
appositional growth
appositional growth
A thin layer of osteoblasts (the bone forming cells) resides on the inner surface of the periosteum. As the osteoblasts lay down more and more osseous tissue, making the bone thicker and wider, osteoclasts come behind from inside the marrow cavity and dissolve some of that bone allowing the marrow cavity to grow as well
Appositional growth results in
production of circumferential lamellae
How many bones to infants have?
270
soft spaces between the skull in infants are called
fontanelles
Fontanelles grow together, now called
cranial sutures
Fontanelles allow
brain to grow fast than body
Mandible is two seperate bones fused along midline, ossified cartilage is called the
mandibular symphysis
Pelvis consists of
2 ox coxae
1 os coxae
fused pubis, ilium, ischium
Everyday bone remodeling repairs
microfractures
Forces that develop bone features
pulling and compression
Pulling forces stimulate
osteoblast activity
Contractile forces stimulate
osteoclast activity
Bone remodeling is important for
mineral release and absorption into bloodstream
Bone remodeling maintains what chemical levels?
calcium and phosphate
Wolff’s Law
bone architecture is determined by mechanical stresses placed on it
Bones increase in density when
mechanical stress is placed on them
Stress lines
trabeculae of spongy bone will increase in density and orient themselves to accommodate increased mechanical stress
When does bone remodeling happen?
Throughout life
Osteoblasts __ bone matrix
synthesizes
Osteoclasts __ bone matrix
dissolve
Creating more bone is called
bone deposition
Removing bone tissue is called
bone resorption
Osteoclast dissolve, increasing what levels
Ca2+
What secretions help break down osseous tissue?
HCl and collagenase
Bone repairs in
8-12 weeks
Blood clot =
Hematoma
Fracture Repair Steps
Hematoma formation and granulation, soft callus formation, hard callus formation, remodeling.
Bone and blood vessels are severed, blood clots around site.
Fibroblasts, osteogenic cells, and blood vessels invade the area creating a soft mass of tissue called GRANULATION TISSUE
Hematoma formation and granulation
Fibroblasts deposit collagen that creates a fibrous patch around the fracture
Soft Callus formation
Osteoblasts lay down a collar of new bone surrounding the fracture called a HARD CALLUS.
The hard callus is the body’s version of a cast that keeps the pieces of bone properly aligned during healing.
At this point the fracture is still fragile and can be re-broken quite easily.
Hard Callus formation
Remodeling
process by which the broken pieces of bone are remodeled and gaps between bone pieces are filled.
Osteoclasts remove small fragments of broken bone and smooth jagged edges.
Osteoblasts enter and lay down a layer of spongy bone to close any gaps (prevents bones from shortening after a fracture)
Spongy bone transitions to compact bone and fracture site is often nearly undetectable
Fibroblasts, osteogenic cells, and blood vessels invade the area creating a soft mass of
Granulation tissue
fibrous patch around the fracture is a
soft callus
osteoblasts lay down collar of new bone called
hard callus
Osteoporosis
Disease in which bones become less dense, very brittle and susceptible to fracture
Osteoporosis literally means
porous bones
What is decreased in Osteoporosis?
Bone mineral density
This is affected most when you have osteoporosis
spongy bone
Risk factors for osteoporosis
Females, Asian or Caucasian, low estrogen levels, poor diet, smoking, sedentary lifestyle, taking glucocorticoids.
Treatments for osteoporosis
Activity, resistance training, diet, supplements, medications to inhibit osteoclast activity,
abnormal bone formation due to lack of Vitamin D, calcitriol, or calcium/phosphate. Weight bearing bones such as the femur often bow in/out due to softness of bone
Rickets