Biology 111 Lecture 10
What are the 3 Types of Cartilage and Where are they Found?
Hyaline: articular surfaces, costal cartilages, respiratory cartilages, nasal cartilages, epiphyseal plates (youth)
Elastic: epiglottis, ear pinnae
Fibrocartilage: menisci, intervertebral discs, pubic symphysis
What are the 7 functions of Bones?
1.Support -For body and soft organs
2.Protection - Protect brain, spinal cord, and vital organs
3.Movement - Levers for muscle action
4.Mineral and growth factor storage - Calcium and phosphorus, and growth factors reservoir
5.Blood cell formation - Hematopoiesis occurs in red marrow cavities of certain bones
6.Triglyceride (fat) storage - Fat, used for an energy source, is stored in bone cavities
7.Hormone production - Osteocalcin secreted by bones helps to regulate insulin secretion, glucose levels, and metabolism
How Many Bones are in the Human body?
206
the Skeleton is divided into two sections called?
Axial (Head, Neck Trunk) Appendicular( Limbs, Arms, and Legs)
What is Compact Bone?
Compact bone: dense outer layer on every bone that appears smooth and solid
What is Spongy Bone?
Spongy bone: made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae
What are the Open spaces Between Trabeculae Filled with?
Open spaces between trabeculae are filled with red or yellow bone marrow
The gross anatomy of all bones consists of
compact bone sandwiching spongy one
What are the two types of membranes?
periosteum and endosteum
What is Periosteum?
Periosteum: white, double-layered membrane that covers external
surfaces except joints
What is Fibrous Layer?
Fibrous layer: outer layer consisting of dense irregular connective
tissue consisting of Sharpey’s fibers that secure to bone matrix
What is Osteogenic Layer?
Osteogenic layer: inner layer abutting bone and contains primitive osteogenic stem cells that gives rise to most all bone cells
What is Endosteum?
Delicate connective tissue membrane covering internal bone surface
Covers trabeculae of spongy bone
Lines canals that pass through compact bone
Like periosteum, contains osteogenic cells that can differentiate into
other bone cells
Where can you find Compact Bone?
Compact bone sandwiched between connective tissue membranes
What do Periosteum and Endosteum do with Compact Bone?
Periosteum covers outside of compact bone, and endosteum covers inside portion of compact bone
Where is Bone Marrow Found?
Bone marrow is scattered throughout spongy bone; no defined marrow cavity
Hyaline Cartilage Covers Area of Bone That?
Hyaline cartilage covers area of bone that is part of a movable joint (articular cartilage)
All Long Bones Have A?
have a shaft (diaphysis),
bone ends (epiphyses), and membranes
What is Diaphysis?
Diaphysis: tubular shaft that forms
long axis of bone
What is Epiphysis
Epiphyses: ends of long bones that consist of compact bone externally and spongy bone internally
What does diaphysis consist of?
Consists of compact bone surrounding central medullary cavity that is filled with yellow marrow in adults
What is between Diaphysis and Epiphysis?
Between diaphysis and epiphysis is epiphyseal line (metaphysis)
Where is Red Bone Marrow Found?
Red marrow is found within trabecular cavities of spongy bone and diploë of flat bones, such as sternum
True or False? In newborns, medullary cavities and all spongy bone contain red marrow
True
In Adults where is Red Bone Marrow Located?
In adults, red marrow is located in heads of femur and humerus, but most active areas of hematopoiesis are flat bone diploë and some irregular bones (such as the hip bone)
If a person is Anemic Yellow Bone Marrow can Convert to?
red, if person becomes anemic
What are the Five Major Cell Types of Bone Tissue?
1. Osteogenic cells
2. Osteoblasts
3. Osteocytes
4. Bone-lining cells
5. Osteoclasts
What are Osteogenic Cells?
Also called osteoprogenitor cells
– Mitotically active stem cells in periosteum and endosteum
– When stimulated, they differentiate into osteoblasts/bone
-lining cells
What are Osteoblasts?
Osteoblasts
– Bone-forming, secrete unmineralized bone matrix called osteoid
§ Osteoid is made up of collagen and calcium-binding proteins – Osteoblasts are actively mitotic
What are Osteocytes?
Osteocytes
– Mature bone cells in lacunae that no longer divide
– Maintain bone matrix and act as stress or strain sensors
§ Respond to mechanical stimuli such as increased force on bone or weightlessness
§ Communicate information to osteoblasts and osteoclasts (cells that destroy bone) so bone remodeling can occur
What are Bone Lining Cells?
Bone-lining cells
– Flat cells on bone surfaces believed to also help maintain matrix (along with osteocytes)
What are Bone Linings cells called on the external surface?
periosteal cells
What are Bone Lining Cells called on the internal surface?
endosteal cells
What are Osteoclasts?
– Giant, multinucleate cells function in bone resorption (breakdown of bone)
– When active, cells are located in depressions called resorption bays
– Cells have ruffled borders that serve to increase surface area for enzyme degradation of bone
§ Also helps seal off area from surrounding matrix
What Does Compact Bone Consist Of?
Compact bone – Consists of:
§ Osteon (Haversian system)
§ Canals and canaliculi
§ Interstitial and circumferential lamellae (layers)
What is an Osteon?
An osteon is the structural unit
of compact bone
– Consists of an elongated cylinder that runs parallel to long axis of bone
-Acts as weight-bearing pillars
What do Lamellae Contain?
Lamellae contain collagen fibers that run in different directions in adjacent rings
Where are Bone Salts Found?
Bone salts are found between collagen fibers
What is a Central Canal?
Central (Haversian) canal runs through core of osteon
- Contains blood vessels and nerve fibers
What are Perforating Canals?
Perforating (Volkmann’s) canals: canals lined with endosteum
that occur at right angles to central canal
-Connect blood vessels and nerves of periosteum, medullary cavity, and central canal
What are Lacunae?
Lacunae: small cavities that contain osteocytes
What are Canaliculi?
Canaliculi: hairlike canals that connect lacunae to each other and to central canal
How do Canaliculi Form?
When matrix hardens and osteocytes are trapped the canaliculi form
Canaliculi Allow?
Allow communication between all osteocytes of osteon and permit
nutrients and wastes to be relayed from one cell to another
Bone is made up of both
Bone is made up of both organic and inorganic components
Organic Components in Bone Include?
Organic components
Includes osteogenic cells, osteoblasts, osteocytes,
bone-lining cells, osteoclasts, and osteoid
Osteocyte makes up ___
Osteoid, which makes up one-third of organic bone extracellular matrix, is secreted by osteoblasts
Osteiod Consists Of?
• Consists of ground substance and collagen fibers, which contribute to high tensile strength and flexibility of bone
InOrganic Compounds in Bone Include?
Inorganic components
– Hydroxyapatites (mineral salts)
- Makeup 65% of bone by mass
- Consist mainly of tiny calcium phosphate crystals in and
around collagen fibers in extracellular matrix
- Responsible for hardness and resistance to compression
Long Bones Grow Lengthwise By?
Interstitial (longitudinal) growth of epiphyseal plate
Bones increase thickness through?
Appositional growth (deposition of bone on surface of bone
Bones stop growing lengthwise during?
Adolescence
Interstitial growth requires presence of?
epiphyseal cartilage in the epiphyseal plate
Epiphyseal plate maintains?
Constant Thickness
– Rate of cartilage growth on one side balanced by bone
replacement on other
Epiphyseal plate closure occurs when
epiphysis and diaphysis fuse
Near end of adolescence what happens to Chondroblasts?
Chondroblasts divide less often
Bones thicken in response to increased?
stress from muscle activity or added weight
Growing bones widen as they lengthen through?
Appositional growth
– Can occur throughout life
Osteoclasts remove bone on?
Endosteal Surface
Osteoblasts beneath periosteum secrete bone?
matrix on external bone
Growth hormone is the most important hormone in stimulating?
most important hormone in stimulating epiphyseal plate activity in infancy and childhood
What does Thyriod Hormone do?
Thyroid hormone: modulates activity of growth hormone, ensuring proper proportions
What does Testosterone do in Bone Growth?
Testosterone (males) and estrogens (females) at puberty: promote adolescent growth spurts
– End growth by inducing epiphyseal plate closure
Excesses or deficits of any hormones can cause?
Abnormal Skeletal Growth
How much Bone Mass is recycled every week?
About 5–7% of bone mass is recycled each week
Spongy is bone replaced every?
Every 3-4 years
Compact bone is replaced?
Every 10 years
Bone remodeling consists of both bone deposit and?
Bone Resorption
What are Remodeling Units?
Packets of adjacent osteoblasts and osteoclasts coordinate remodeling process
Resorption is a function of?
Osteoclasts
What Happens Duirng Resoprtion?
-Dig depressions or grooves as they break down matrix
– Secrete lysosomal enzymes and protons (H+) that digest matrix
– Acidity converts calcium salts to soluble forms
Osteoclasts also phagocytize?
Demineralized matrix and dead osteocytes
Digested products are transcytosed across cell and?
Released into interstitial fluid and then into blood
Once resorption is complete, Osteoclasts undergo?
Apoptosis
Osteoclast activation involves?
PTH (parathyroid hormone) and immune T cell proteins
New bone matrix is deposited by?
Osteoblasts
What is an Osteoid Seam?
Osteoid seam: band of unmineralized bone matrix that marks area of new matrix
What is Calcification Front?
Abrupt transition zone between osteoid seam and older mineralized bone
Trigger for deposit not confirmed but may include?
– Mechanical signals
– Increased concentrations of calcium and phosphate ions for hydroxyapatite formation
– Matrix proteins that bind and concentrate calcium
– Appropriate amount of enzyme alkaline phosphatase for
mineralization
Remodeling occurs continuously but is regulated by?
Genetic factors and two control loops
Give an Example of Hormonal Controls?
Hormonal controls
– Parathyroidhormone(PTH):produced by parathyroid glands in response to
low blood calcium levels (negative feedback loop)
- Stimulates osteoclasts to resorb bone
- Calcium is released into blood, raising levels
- PTH secretion stops when homeostatic calcium levels are reached
What is Calcitonin?
Produced by parafollicular cells of thyroid gland in response to high levels of blood calcium levels
-Effects are negligible, but at high pharmacological doses it can lower blood calcium levels temporarily
Bones reflect stresses they encounter
-Bones are stressed when weight bears on them or muscles pull
on them
- Stress is usually off center, so bones tend to bend
-Bending compresses one side, stretches other side
– Diaphysis is thickest where bending stresses are greatest
Handedness (right- or left-handed) results in?
thicker andnstronger bone of the corresponding upper limb
Curved bones are thickest where?
Most likely to buckle
Large, bony projections occur where?
Heavy, active muscles attach
Mechanical stress causes remodeling by producing?
Electrical signals when bone is deformed
– Compressed and stretched regions are oppositely charged
– Compression/tension changes fluid flows within canaliculi, which may also stimulate remodeling
Hormonal controls determine if and when remodeling occurs in response to?
Changing blood calcium levels, BUT mechanical stress determines where it occurs
Fractures are?
Breaks
– During youth, most fractures result from trauma
– In old age, most result from weakness due to bone thinning
How many Fracture Classifications are there?
3
Position of bone ends after?
Fracture
Nondisplaced: ends retain?
Displaced: ends are out of?
Nondisplaced: ends retain normal position
Displaced: ends are out of normal alignment
Complete is broken? Incomplete is not?
Complete: broken all the way through
Incomplete: not broken all the way through
Open skin is? Closed skin is not?
-Open (compound): skin is penetrated
- Closed (simple): skin is not penetrated
3 Fracture Classifications are?
Position, Completeness, Pentrated
What is a Communited Fracture?
Fragments break into three or more pieces, most common is aged as their bones are more brittle.
What is a Compression Fracture?
Bone is crushed, more common in porous bones, subjected to extreme tramua as in fall
What is a Spiral Fracture?
Ragged break occurs when excessive twisting forces are applied to a bone
-Common Sports Fracture
What is an Epiphyseal Fracture?
Epiphysis seperates from Diaphysis along the Epiphyseal Plate
-Tends to occur where cartilage cells are dying and calcification of the matrix is occuring
What is a Depressed Fracture?
Broken Bone Portion is pressed inward
-Typical Skull Fracture