THEA 101 Lecture Notes - Lecture 4: Bone Remodeling, Osteoporosis, Pituitary Adenoma
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Chapter 6: Bone Tissue
Skeletal System:
Skeletal system is made up of several tissues
working together:
Osseous tissue
Cartilage
Dense connective tissue
Epithelium
Adipose
Nervous tissue
Bones form the internal structural support system
for the human body
Initially made up of cartilage then replaced by
bone
Although cartilage still remains in some
areas
What are the functions of bone?
Gives support and provides a site for muscle
attachment through tendons
Protection
Protects visceral organs (ex. Ribcage
protects thoracic organs)
Movement
Bones act as levers attached to muscle
tissue to provide locomotion
Mineral and Growth Factor Storage
Reservoir for minerals: Calcium (muscle
contractions/nerve impulses to go
through) and Phosphate that are
deposited in bone and released into
bloodstream when needed
Blood Cell Formation
Hematopoiesis: formation of red blood
cells, white blood cells and platelets from
red bone marrow of certain bones
In newborns, all marrow is red and
produces RBCs
Fat Storage
In adults, some red marrow is replaced by
yellow marrow (adipocytes) and used to
store triglyercides (fat)
Classification of Bones
There are 206 bones in the adult human skeleton
Skeleton is divided into:
Axial Skeleton
Forms the long axis of the body
Skull
Vertebral column
Rib cage
Appendicular Skeleton
Forms bones of upper and lower limbs
and girdles
Shoulder girdle
Bones of arms, hands
Pelvic girdle (hips)
Bones of the legs, feet
Bones can be classified by size and shape:
Long Bones
Elongated (longer than wide)
Mostly compact bone with some spongy
bone
All limb bones except patella, bones of
wrist and ankle
Short Bones
Cube-shaped
Spongy bone inside with compact bone
surrounding
Bones of wrist and ankle (carpals/tarsals)
Flat Bones
Thin and flat
2 thin layers of compact bone with
spongy bone inside
Sternum, scapula, ribs, skull bones,
mantile.
Irregular Bones
Irregularly shaped
Variable amount of compact and spongy
bone
Vertebrae, calcaneus
Sesamoid Bones short bones that form IN
tendons
Ex. patella (kneecap), small bones
in the hand and foot
Wormian Bones
Bones that are formed between cranial
sutures
Bone Markings
Projections, depressions and openings in the bone
serve as attachment sites for: (the attachments to
whatever.)
Muscles
Tendons
Ligaments
Joint surfaces
Conduits for blood vessels and nerves: in
foramen
Know FOSSA.
Compact v. Spongy Bone
All bones have a smooth solid outer surface:
compact bone (lamellar bone)
Internal to the compact bone is spongy bone
(woven)
Honeycomb of small trabeculae (lattice of
bone, little dots)
Allows for lots of blood vessels to come
in.
Hematopoietic Tissue
Blood cell forming tissues
Red marrow is found within the trabecular
cavities of spongy bone
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Newborns: red marrow fills both the
trabecular cavities and the medullary
cavities
Children and adults: medullary cavities
are filled with yellow marrow (fat)
Sternum, hip bones, ribs, vertebrae and
proximal ends of humerus and femur are sites
of red bone marrow in the adult.
These are locations used for obtaining
bone marrow samples when problems
with blood forming tissues are suspected
Anatomy of Long Bones
Diaphysis: shaft
Mostly compact bone surrounding the
medullary (marrow) cavity
Medullary cavity contains blood
vessels and yellow marrow (fat)
in the adult
Epiphysis: distal (bottom of
bone) and proximal bone
ends(head or bone)
Compact bone exterior/Spongy bone
interior
Joint surface covered with articular
cartilage
Hyaline cartilage that reduces
friction and absorbs shock upon
movement
Metaphysis: regions between the
diaphysis and epiphysis
Epiphyseal plate/line
Plate: Disc of hyaline cartilage
that grows during childhood to
lengthen the bone
Line: In adults; cartilage is
replaced by bone
Membranes of Bone
Periosteum
Sheath that surrounds the external surface
of the bone EXCEPT at the joint
Outer fibrous layer: dense
irregular CT, blood
vessels/nerves travel,
attachement site.
Inner osteogenic layer:
osteogenic cells, osteoblasts
Allows the bone to grow
in thickness
Protects bone, assists in repair, nourishes
bones and serves as attachment points for
ligaments and tendons
Contains nerves and blood vessels
Secured to the bone via perforating
fibers
Endosteum
Thin membrane that covers the
trabeculae of spongy bone and lines
canals of compact bone
Contains osteoblasts and osteoclasts
Anatomy of Short, Flat and Irregular Bones
All consist of a compact/spongy bone sandwich
Compact bone on the outsides
Covered by periosteum
Spongy bone on the inside
Covered by endosteum
Chemical Composition of Bone
Osseous Tissue (bone)
Bone matrix is similar to cartilage but is
hard due to Calcium Salts
25% water, 25% collagen fibers, 50%
crystalized salts
Organic components:
Cells
Osteoid
Ground substance
Collagen fibers
Inorganic components:
Hydroxyapatites (the picture) ----------->
Calcium phosphates
Calcium hydroxide
Calcium carbonate
Fluoride, sulfate, potassium,
magnesium
Calcification: As the mineral
salts are deposited in the matrix
around the collagen fibers, they
crystalize making the matrix hard
Mineral salts make the bone hard
Collagen fibers give the bone its
“flexibility”
Provide tensile strength
Bone Histology
4 major cell types in bone tissue: GPCC from G-> P->
C
Osteogenic (osteoprogenitor) cells
Stem cells derived from mesenchyme -
mitotically active
Found in the inner periosteum,
endosteum, canals of bone containing
blood vessels
Osteoblasts
Osteogenic cells that have differentiated
(committed to be a bone cell)
Bone-forming cells: synthesize matrix
(collagen fibers and organic components)
Initiate calcification
Eventually surround themselves with
matrix and become trapped
Lots of ribosomes + cytoplasm
Osteocytes
Mature bone cells that reside in lacunae
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Document Summary
Skeletal system is made up of several tissues working together: Bones form the internal structural support system for the human body. Initially made up of cartilage then replaced by bone. Bones can be classified by size and shape: Mostly compact bone with some spongy bone. All limb bones except patella, bones of wrist and ankle. Spongy bone inside with compact bone surrounding. Gives support and provides a site for muscle attachment through tendons. Bones act as levers attached to muscle tissue to provide locomotion. 2 thin layers of compact bone with spongy bone inside. Variable amount of compact and spongy bone. Sesamoid bones short bones that form in. Reservoir for minerals: calcium (muscle tendons contractions/nerve impulses to go through) and phosphate that are deposited in bone and released into bloodstream when needed. Hematopoiesis: formation of red blood cells, white blood cells and platelets from red bone marrow of certain bones. In newborns, all marrow is red and produces rbcs.
