Chapter 6, 7, 8 - The Skeletal-Bone Tissue, Axial Skeleton, and Appendicular Skeleton

How many bones are in the Axial Skeleton?

80 bones

How many bones are in the Appendicular Skeleton?

126 bones

What bones are in the Axial Skeleton?

the skull (cranial and facial bones), hyoid bone, auditory ossicles, the vertebral column, and the thorax (sternum and ribs)

What bones are in the Appendicular Skeleton?

the pectoral girdles (clavicle and scapula), upper limbs (humerus, ulna, radius, carpals, metacarpals, and phalanges), pelvic girdles (os coxa), and lower limbs (femur, patella, tibia, tarsals, metatarsals, and phalanges)

What are the functions of the bone and skeletal system?

- protects internal organs

- stores and releases fats

- produces blood cells

- stores and releases minerals

- facilitates movement

- supports the body

What are the types of bones?

long bones, flat bones, short bones, irregular bones, and sesamoid bones

What is an example of a long bone?

the humerus

What is an example of a flat bone?

the sternum

What is an example of a short bone?

the trapezoid or wrist bone

What is an example of an irregular bone?

the vertebra

What is an example of a sesamoid bone?

the patella

_____ and _____ are needed in larger quantities when bones are growing

calcium ; phosphorus

What is the diaphysis of a bone?

the long, cylindrical, main portion

What is the epiphysis of a bone?

the proximal and distal ends of the bone

What is the metaphysis of a bone?

the regions between diaphysis and epiphysis

What is the articular cartilage of a bone?

the thin layer of hyaline cartilage covering the epiphysis where it articulates with another bone

What is the periosteum of a bone?

the tough connective tissue covering of the bone anywhere there isn’t articular cartilage

What is the medullary cavity of a bone?

the hallow cavity within the diaphysis that contains the fatty yellow bone marrow and numerous blood vessels

What is the endosteum of a bone?

the thin membrane that lines the medullary cavity and internal spaces of spongy bone

What are the 4 types of osseous (bone) tissue?

osteogenic cell, osteoblasts, osteocytes, and osteoclasts

what is the osteogenic cell?

unspecialized stem cells; divide and transform into bone-building osteoblasts

what are osteoblasts?

bone-building cells (B for Build); forms bone matrix

what are osteocytes?

mature bone cells; maintains bone tissue

what are osteoclasts?

derived from as many as 50 monocytes (type of WBC) fusing together —> in endosteum; resorbs bone

What is bone deposition?

the process where osteoblasts construct new bone tissue by secreting the organic matrix and depositing minerals into it

What is bone resportion?

the process where osteoclasts break down bone tissue, dissolving its minerals and digesting its organic matrix

What is compact bone?

the dense, outer layer of the bones that provide strength and protection; takes up to 80% of skeleton

What is spongy bone?

found at the ends of long bones (femur and humerus) and in the middle of flat bones (skull and sternum) —> lighter and more porous —> contributes to bone flexibility and weight reduction (contains bone marrow; contains up to 20% of the skeleton

Compact Bone Tissue

located: beneath the periosteum of all bones (diaphysis of long bones)

function: structural support, protection, and leverage for movement

What is the osteon?

the fundamental structural unit

- concentric bone lamellae (rings)

What is the osteonic (central) canal?

blood vessels

- the central canal and haversian canal

What are the bone lacunae?

small spaces

- where osteocytes reside

what is bone canaliculi?

small channels

- interconnected canals between bone lacunae and osteonic canals

- routes for nutrients and O₂ to reach osteocytes

- Finger-like projections of osteocytes

- Removal of wastes

Where is spongy bone tissue located?

in the epiphysis of the long bone, vertebrae, short bones (carpals and tarsals), flat bones (sternum, ribs, and skull bones), and pelvic bones

- interior of the compact bone

Spongy Bone Trabeculae

- concentric bone lamellae

- osteocytes within bone lacuna

- bone canaliculi

Red Bone Marrow

- appears red due to rich blood supply

- hematopoietic tissue = blood cell production

- consists of: red blood cells (O₂), white blood cells, and platelets

- located: mainly in spongy bone

- more active in youth

Yellow Bone Marrow

- appears yellow due to higher fat concentration

- stores triglycerides

- located: in medullary cavity of long bones

- becomes predominant as we age

What do bone scans detect?

fractures, infections, cancer/tumors, and arthritis

What do bone density scans detect?

fracture risk assessment, osteopenia, and osteoporosis

What does intramembranous ossification do?

develops bone directly from a sheet of embryonic connective tissue

What does endochondral ossification do?

builds bone by replacing an existing hyaline cartilage model

What are the steps of endochondral ossification?

1. development of cartilage

2. growth of cartilage model

3. development of primary ossification center

4. development of medullary cavity

5. development of secondary ossification centers

6. formation of articular cartilage and epiphyseal plates

Intramembranous ossification

flat bones of the skull, facial bones, the mandible, and the clavicle

Endochondral ossification

most remaining of the skull (long bones, short bones, vertebrae, and ribs)

Interstitial Growth

growth in length

- growth plate of cartilage on the epiphyseal growth plate

- replacement of cartilage by bone tissue in epiphyseal plate

Appositional Growth

growth in thickness

- osteoblasts in periosteum build new bone matrix on outer surface (increase bone diameter)

- osteoclasts in endosteum resorb bone from inner surface (prevents excessive thickness)

What is the epiphyseal plate and where is it located?

the hyaline cartilage in the metaphysisW

What are the 5 zones of the epiphyseal plate?

1. zone of Resting cartilage

2. zone of Proliferating cartilage

3. Zone of Hypertrophic cartilage

4. Zone of Calcified cartilage

5. Zone of (endochondral) Ossification

What are some factors affecting bone growth and remodeling?

parathyroid hormone (raises blood for calcium levels (PTH)) and calcitonin (lowers blood calcium levels)

PTH deficiency

neuromuscular irritability and paresthesia

PTH excess

kidney stones, bone damage, abdominal pain, and central nervous system depressions

CT deficiency or excess

no clinical effects or main issues

Vitamin C

deficiency = gum disease, tooth loosening, and tooth loss

Vitamin A

deficiency = disrupts differentiation of bone cells (osteopetrosis), underdeveloped tooth enamel —> increased cavities and gum disease

Vitamin D

deficiency = impairs body’s ability to absorb calcium and P^3-, weakened bones —> osteoporosis —> prone to fractures, and tooth decay and periodontal disease

Effects of Hypersecretion of GH

giantism (occurs during childhood) and acromegaly (occurs during adulthood)

What is osteoporosis?

a metabolic bone disease with a severe loss of bone mineral density and structural degradation

- bones are highly porous, fragile, and prone to fractures

What is osteopenia?

a clinical condition where bone mineral density is lower than normal peak levels

- not severe enough to be classified as osteoporosis

What is osteogenesis imperfecta?

a genetic disorder caused by a defect in collagen synthesis

- extremely fragile bones that fracture easily, often while little or no apparent trauma

What is achondroplasia?

a genetic form of short-limbed dwarfism caused by a mutation that impairs endochondral ossification

- prevents long bones of the arms and legs from growing normally

Gigantism

a rare condition caused by the hypersecretion of growth hormones during childhood

- leads to excessive longitudinal bone growth and abnormal height before growth plate fuse

Pituitary Dwarfism

a condition of severely stunted growth caused by a deficiency of growth hormone during childhood

- results in a short stature but normally proportioned body parts

Phocomelia

a rare congenital deformity characterized by severe underdevelopment or absence of the long bones in the limbs

- causes the hand or foot to be attached very close to the trunk

Open (Compound) Fracture

broken bone protrudes through skin

Greenstick Fracture

partial fracture: one side of the bone is broken and the other side bends —> only in children

Comminuted Fracture

bone is splintered, crushed, or broken into pieces: smaller bone fragments lie between 2 main fragments

Impacted Fracture

one end of fractured bone is forcefully driven into interior of the other

Pott Fracture

fracture of the distal end of the fibula, with serious injury of distal tibial articulation

Colles Fracture

fracture of the distal end of the radius in which distal fragment is displaced posteriorly

Vertebral Compression Fracture (VCF)

vertebral body is fractured and becomes compressed into a wedge-shape

Stress Fracture

a tiny crack in a bone, usually caused by overuse or repetitive stress

- common in weight-bearing bones of lower legs and foot

What are the steps of bone repair?

1. Reactive phase - formation of fibrous cartilage callus formation (soft cartilage and fibrous tissue that build and act as a bridge while the healing process goes on)

2. Reparative phase - bony callus formation (hard spongy bone)

3. Bone remodeling phase

What are factors that affect bone repair?

- osteoporosis —> slower healing

- age —> bone healing slows down with age

- nutrition —> deficiencies in calcium, vitamin D, and proteins

- lifestyle factors —> smoking and excess alcohol use —> slows it down

The _______ derives from the ______ and the _______.

axial skeleton ; mesoderm ; ectoderm

The ___________ derives from just the _______.

appendicular skeleton ; mesoderm

The ___________ derives the _________.

neurocranium (mesoderm) ; cranial bones

The ___________ derives the _________.

viscerocranium (ectoderm) ; facial bones

Flathead Syndrome

a flat spot on a baby’s skull due to prolonged, repeated pressure on one part of their soft head

- cranial remodeling

Cranial Stenosis

a premature fusion of one or more skull bones in an infant —> prevents normal skull growth and impacts brain development

- surgery

Spinal Bifida

a birth defect of neural tube —> spinal cord does not completely close during pregnancy

Cleft Palate

palatine bones and other tissues do not fuse together properly during fetal development

- surgery