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Skeletal System Summary [Essential of Human Anatomy and Physiology]
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- Nursing
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- Trent University (TrentU )
Skeletal System Summary [Essential of Human Anatomy and Physiology]
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SKELETAL SYSTEM c. Bone substance – EM and cells§ It consists of the bone, cartilage, tendons and
ligaments. Histology of Bone
§ Skeleton; dried (Greek) Osteoblasts – bone-forming cells; repair and remodeling
of bone
Functions (S2PMB)
1. Support Osteocytes – bone cells located between the lamellae
2. Protection (thins sheets of EM)
3. Movement
4. Storage Lacunae – spaces within the lamellae
5. Blood cell production
Canaliculi – tiny canals within the lamellae
Extracellular Matrix
§ Composed of connective tissues Types of Bone Tissue
a. Compact bone
Collagen – tough ropelike protein § Forms most of the diaphysis of long bones
§ Central Canal / Haversian Canal – concentric
Proteoglycans – large molecules consisting of rings that contains blood vessels; ‘bull’s eye’
polysaccharides attached to core proteins § Osteon / Haversian System – central canal +
lamellae + osteocytes
Tendons & Ligaments – large amounts of collagen fiber
b. Spongy bone
Cartilage – contains collagen & proteoglycans § Located mainly in the epiphyses of long bones
§ Forms the interior of all other bones
Bone – contains collagen and minerals (Calcium & § Consists of trabeculae (interconnecting rods,
Phosphate) plates of bone) without central canals
Hydroxyapatite – calcium phosphate crystals Bone Ossification
Ossification – formation of bone by osteoblasts
General Features of Bone
§ Long bones; upper and lower limbs Types of Ossification
§ Short bones; wrist and ankle a. Intramembranous ossification – osteoblasts
§ begin to produce bone in connective tissue
§ Irregular bones; vertebrae and facial bones Ø Ossification centers – where
intramembranous ossification begins
Long Bones
a) Diaphysis – central shaft b. Endochondral ossification – bone formation
b) Epiphysis – ends occurs inside the cartilage; bones at the base of
c) Epiphyseal plates – growth plate; where the the skull and remaining skeletal system are
bone grows in length formed
Ø Chondrocytes – cartilage cells; increase
Articular cartilage – covers the ends of the epiphyses in no., enlarge, and die
Epiphyseal line – bone growth stops and the epiphyseal Primary ossification center – where bone first begins to
plate is replaced by bone appear
Medullary Cavity – large cavity in the diaphysis; Osteoclasts – cells that remove calcified cartilage matrix
contains the marrow
Secondary ossification center – form in the epiphyses
Marrow – soft tissue within the cavity
Bone Growth
Yellow Marrow – consists of adipose tissue (fat) § Deposition of new bone lamellae onto existing
bone
Red Marrow – consists of bone forming cells; site of § Bone elongation occurs at the epiphyseal plate;
blood formation leads to increase in height (endochondral
ossification)
Layers of a Bone § Chondrocytes proliferate, enlarge, die, and are
a. Periosteum – outermost layer; surround the replaced by bone
diaphysis; contain blood vessels, nerves,
osteoblasts Appositional growth – increase in bone width or
diameter
b. Endosteum – innermost layer; lines the
medullary cavity (thinner connective tissue)
M o r a n o , M . A .
, Bone Remodeling AXIAL SKELETON
§ Removal of existing bone by osteoclasts § Composed of the skull, vertebral column, and
§ Deposition of new bone by osteoblasts thoracic cage
§ Responsible for change in bone shape, bone § Form the longitudinal axis of the body
adjustment, repair, and calcium ion regulation
I. Skull
Bone Repair § 22 bones
§ Clot is formed in the damaged area
§ Blood vessels and cells invade the clot and form Braincase
a callus (network of fibers and islets of cartilage) § 8 bones
§ Osteoblasts enter the callus and from a spongy § Covers and protects the fragile brain tissue
bone
§ Bone is slowly remodeled to compact bone 1. Frontal Bone – forehead, bony projections
under the eyebrow, part of the eye’s orbit
Bone and Calcium Homeostasis
§ Osteoclasts remove calcium = blood calcium 2 - 3. Parietal Bone (paired) – the superior and
levels increases lateral walls of the cranium; coronal suture
§ Osteoblasts deposit calcium = blood calcium
levels decrease 4 - 5. Temporal Bone (paired) – lies inferior to
the parietal bone; squamous suture
Hormones that maintain Calcium Homeostasis Ø External Auditory Meatus (EAM) – a
1. Parathyroid hormone (PTH) canal that leads to the eardrum and the
§ Parathyroid gland; middle ear
§ Increase bone breakdown & increase blood Ø Styloid process – a sharp, needlelike
calcium levels; structure located inferior to the EAM
§ Stimulates the kidneys to from active vitamin D Ø Zygomatic process – a bridge of bone
that joins with the cheekbone anteriorly
2. Calcitonin Ø Mastoid Process – a rough projection
§ Thyroid gland posterior and inferior to the EAM
§ Decrease bone breakdown and decrease blood
calcium levels 6. Occipital Bone – inferior and posterior bone
of the cranium; lambdoid suture
General Considerations of Bone Anatomy Ø Foramen magnum – where the spinal
§ 206 bones = adult cord joins the brain
§ 276 bones = newborn baby Ø Occipital condyles –rests on the first
vertebra of the vertebral column
Foramen – hole in a bone Ø Foramen ovale – allows the fiber of
cranial nerve 5 to pass
Canal / Meatus – elongated hole in a tunnel like body
7. Sphenoid Bone – butterfly-shaped bone that
Fossa – depression in a bone spans the width of the skull
Ø Sella Turtica – saddle-shaped structure
Tubercle / Tuberosity – lump on a bone at the central region; contains the
pituitary gand
Process – projection from a bone
8. Ethmoid Bone –
irregularly shaped bone that
Condyle – end of a bine that forms a joint with another lies anterior to the sphenoid bone
bone
Facial bones
Facet – small flattened articular surface § 14 bones; 13 solidly connected, 1 movable
(mandible)
Crest – prominent ridge § Holds the facial muscles in place
§ Joined together by sutures (interlocking,
Trochanter – tuberosity found only on proximal femur immovable)
Fissure – cleft 1-2. Maxillae – main bones of the face; carries
the upper teeth
Sinus – cavity
3-4. Palatine Bones – lies posterior to the
Suture – a joint uniting the bones of the skull palatine processes of the maxilla
5-6. Zygomatic Bones – cheekbones
M o r a n o , M . A .
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