Exam 2 - bone tissue - Biological Sciences 201 with Washo-krupp at Arizona State University - Tempe

Jose M.

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Individual bones are made of:

Bone tissue
Bone marrow
Cartilage
Periosteum

What type of tissue are bones?

Connective tissue

List the functions of the skeletal system

Support
Protection
Movement
Blood formation
Mineral reservoir
pH balance
Detoxification

Examples of Long bones

Radius
Ulna
Femur

Examples of short bones

Talus
Capitate (carpal) bone

Examples of flat bones

Scapula
Sternum

Examples of irregular bones

Sphenoid bone
Vertebra

Explain how the structure of a flat bone is conducive to protection

Blow to flat bone may fracture outer layer and dipole but does not harm the inner compact bone

Name the type of bone and its structures

Long

Articular cartilage 7. Nutrient foramen
Red bone marrow 8. Site of endosteum
Epipyseal line 9. Compact bone
Marrow cavity 10. Spongy bone
Yellow bone marrow 11. Epipysis
Periosteum 12. Diaphysis

Cells of Osseous Tissue

1. Osteogenic

2. Osteoblasts

3. Osteocytes

4. Osteoclasts

Describe the osteogenic cell

Develops into an osteoblast, undifferentiated cells
Reside in teh endosteum or periosteum

Describe an Osteoblast

Cells that build bone (Bone Formation)
. Synthesize organ components for the ECM (Extracellular Matrix).
Form organic matter of matrix & help to mineralize it in response to stress or fractures

Describe an Osteocyte

Osteoblasts that have become trapped

Reside in lacunae - connected to each other via canaliculi

Signal osteoclasts/osteoblasts about mechanical stress

Describe the Osteoclasts

Bone dissolving cells
Develop in bone marrow by the fusion of the same stem cells that give rise to monocytes of the blood
Reside in pits called resorption bays that they have eaten into the surface of the bone

Describe the organic and inorganic components of bone

Dry weight is 1/3 organic and 2/3 inorganic matter

Organic matter: Collagen, glycosaminoglycans, proteoglycans & glycoproteins
Inorganic matter: 85%-Hydoxyapatite - Crystallized calcium phosphate salt, 10% - Calcium carbonate, Other minerals

Combination provides strength and resilience

Minerals resist compression, collagen resists tension

image bone_without_mineral-1446C71AED34D4C6754-thumb for term side of card

This is a bone without _______

Minerals

This is a bone without _______

Collagen

Explain the importance of a combination of organic and inorganic matter in bones

Collagen (organic) resists tension
Minerals (inorganic) resist compression

Describe Rickets

Deformed bones of the lower extremities
Usually seen in children.
Cause by defective mineralization in bones

Vitamin D deficiency.

Describe osteomalacia

Adult form of Rickets

Bones are categorized by 4 shapes:

Long
Short
Flat
Irregular

Name the bone and its structures

Compact bone

Outer lamellae 5. Endosteum
Osteon 6. Lacuna
Haversian canal 7. Spongy bone
Periosteum 8. Perforating canal

What are the functions of the structures of a compact bone?

Osteons = cylinders of tissue formed from layers of matrix concentrically arranged around a blood vessel

Lamelle = individual layers
Haversian canal = holds blood vessels

Perforating canals = branches of nutrient arteries that run perpendicular to the haversian canals

Describe Spongy bone

Spongelike appearance formed by rods and plates of bone called _trabecule_

spines, rods & plates spaces filled with red bone marrow
Trabeculae have few osteons or haversian canals

no osteocyte is far from blood of bone marrow

Provides strength with little weight

trabeculae develop along bone’s lines of stress

Explain the advantages to having both compact and spongy bone

Compact bone tissue gives bone its strength. A skeleton made completely of compact bone would be too heavy to move.
Spongy bone fills in the bone without adding an excessive amount of weight. A skeleton made completely of spongy bone woud be too fragile.

Characterize the appearance and function of three types of bone marrow

Red marrow (for blood cell formation) in infants. found in most reticular fibers and immature cells
Yellow marrow (mostly fat) in adults; Storage for adipose tissue
Gelatinous marrow - Yellow marrow replaced with reddish jelly

Articular cartilage

Covers the epiphyses to provide friction-free movement in joints

Epiphyseal plate

(Growth plate) - layer of hyaline cartilage that allows the diaphysis of the bone to grow in length

List factors that affect bone growth

Forces applied to skeleton
Nutrition
Gender
Height
Race
Weight

Compare interstitial and appositional bone growth

Interstitial growth - bones increase in length at epiphyseal plate
Appositional growth - bones increase in width (mature bone only)

Compare an contrast achondroplasia and hypo pituitary dwarfism

Achondroplasia is a most common form of dwarfism, where is autosomal dominant but can be from mutation.
Hypopituitary dwarfism is a more proportionate dwarfism, everything aligns more together and it looks more like the body if a child

Describe bone resorption

Minerals dissolved back into solution of body fluids when concentration is LOW
osteoclasts speed this process. osteoclasts release lysosomal enzymes that digest organic matrix and HCl that converts Ca salts into soluble forms

Ectopic ossification

Osseous tissue forming in places other than bone.

A calcified mass in normally soft tissue is a calculus

List the functions of calcium and phosphate in the body

Phosphate is a component of DNA, RNA, ATP, phospholipids, & acid-base buffers

85-90% in bones

Calcium is needed for
Communication between neurons
muscle contraction
blood clotting
exocytosis – movement of substances out of a cell

99% in bones

Describe hypercalcemia and hypocalcemia

Hypocalcemia - deficiency of blood calcium

Causes excessive excitability of nervous system leading to muscle spasms, tremors or tetanus.
Caused by vitamin D deficiency, diarrhea, pregnancy, lactation, underaction/removal of parathyroid glands

Hypercalcemia – excessive blood calcium (rare)

Depresses nervous system muscle weakness, sluggish reflexes, cardiac arrest
Homeostasis depends on: calcitriol, calcitonin & PTH

List the three main hormones involved in calcium homeostasis and explain the effects of each in detail

1. Parathyroid hormone which is synthesized in parathyroid gland. Released when calcium blood level is too low. Inhibits activity of osteoblasts

2. Calcitriol production is feedback regulated. stimulates small intestine to absorb calcium & phosphate. Promotes osteoclast activity.

3. Calcitonin secreted by the thyroid gland when calcium concentration rises too high. Reduces osteoclasts and increases number if osteoblasts.

Explain the effects of estrogen and anabolic steroids on bone growth

Adolescent girls grow faster than boys & reach their full height earlier due to estrogen
Anabolic steroids may cause premature closure of growth plate producing short adult stature

Compare stress fractures and pathological fractures

Stress fracture is a break caused by abnormal trauma to a bone
Pathological fracture is a break in a bone weakened by some other disease

List and characterize the different types of bone fractures

Closed (simple or non-displaced) – skin is not broken
Open (compound or displaced) – bone protrudes from skin
Complete – broken in _2_ or more pieces
Incomplete – extends only partway (pieces remain joined)
Greenstick – one side bent, incomplete fracture on other
Hairline – fine crack
Comminuted – broken in _3_ or more pieces
Linear –parallel along the long axis of the bone
Transverse – perpendicular to long axis of bone
Oblique – diagonal (between linear & transverse)
Spiral – result of a twisting stress

Explain the healing process of fractures

Fracture _hematoma: broken vessels form a blood clot
Ganulation tissue: fibrous tissue formed by fibroblasts & infiltrated by capillaries
Callus formation: soft callus of fibrocartilage replaced by hard callus of bone in 6 week
Remodeling: Occurs over next 6 months as spongy bone is replaced with compact bone

Describe the treatments for fractures

Orthopedics_ = branch of medicine that deals with the prevention & correction of injuries and disorders of the bones, joints & muscles
Closed reduction: fragments are aligned with manipulation & casted

Open reduction: surgical exposure & repair with plates & screws

Traction is not used in elderly due to risks of long-term confinement to bed

Electrical stimulation is used on fractures that take longer than 2 months to heal

Characterize osteoporosis and describe the causes

Most common bone disease

Bones lose mass & become brittle due to loss of both organic matrix & minerals
Risk of hip, wrist & vertebral fracture. lead to fatal complications: pneumonia. Widow’s hump is deformed spine. Postmenopausal caucasian women at greatest risk. by age 70, average loss is 30% of bone mass

Osteoporosis treatments

Estrogen replacement therapy (_ERT_): slows bone resorption. Increases risk of breast cancer, stroke, and heart disease
Drugs: Fosamax, Actonel destroy osteoclasts
PTH: slows bone loss if given as daily injection. Forteo (PTH derivative) increases density by 10% in 1 year

May promote bone cancer so use is limited to 2 years

Best treatment is prevention: exercise & good bone-building diet between ages 25-40

Osteomyelitis

Infection causes inflammation of osseous tissue and bone marrow
Fatal before widespread use of antibiotics

Osteoma

Benign bone tumor

Osteochondroma

Benign tumor of the bone and cartilage

Osteosarcoma

bone cancer

deadly – untreated = death in 1 year
most often in males 10-25 years

Chondrosarcoma

Slow-growing cancer of hyaline cartilage

C) Compare intramembranous and endochondral ossification.

Intramembranous

Develops within fibrous sheet

Produces: Flat skull bones, Most of clavicle

4stages

Condensation of mesenchyme into soft sheet permeated with blood vessels

Desposition of osteoid tissue by osteoblasts on mesenchyme surface; entrapment of first osteocytes; formation of periosteum.

Bony trebeculae formed by continued mineral deposition; creation of spongy bone

Surface of bone filled in by bone deposition, converting spongy bone to compact bone. Spongy bone remain in middle layer.Definition

Endochondrial

-Bone develops from pre-existing model composed of hyaline cartilage

-Applies to most bones of the body: vertebra, ribs, sternum, scapula, pelvis, limb bones

6 stages

Early Cartilage Model

Formation of primary ossification center, bony collar, and periosteum.

Vascular invasion, formation of primary marrow cavity, and appearance of secondary ossification center

-osteoclasts digest bone in center to create marrow cavity.

-osteoblasts deposit bone tissue

Bone at birth with enlarged primary marrow cavity and appearance of secondary marrow cavity in one epiphysis

Bone of child, with epiphyseal plate at distal end.

-epiphysis fills with spongy bone then cartilage is limited to articular cartilage and epiphyseal plates.

Adult bone, with a single marrow cavity and closed epiphyseal plate.

Related Textbooks

Anatomy & Physiology: The Unity of Form and Function

Related Textbooks

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