Skeletal System300 baby bones206 adult bones

>1/2 are in hands & feet

The giraffe has the same number of bones in its neck as a human: seven in total.

Longest bone= femur

Smallest bone= inner ear (hammer, anvil, stirrup)

More Fun Facts

Bone is made of the same type of minerals as limestone.

The long horned ram can take a head butt at 25 mph. The human skull will fracture at 5mph.

The only bone in the human body not connected to another is the hyoid, a V-shaped bone located at the base of the tongue

Enamel is the hardest substance in the human body

The strongest bone in the body is hollow and it is stronger than concrete - femur

Functions of Skeletal System

• Support• Protection• Movement• Hematopoiesis• Reservoir for minerals and adipose tissue

80 bones

126 bones

Skull – 22 bones Cranium – 8 Facial - 14Inner

ear - 3

Vertebral Column - 32

Thorax - 27

Upper limb – 30Shoulder girdle - 2

Lower limb – 29Pelvic girdle – 6

Iliac crest

Thoracic Cage27 bones

Vertebral Column32 bones

Abnormal Spinal Curvatures

Lordosis Kyphosis Scoliosis

The Hand27 bones

The Foot26 bones

Arches of the Foot

Ethmoid

Ethmoid

Foramen – For nerves and vessels

The Skull22 bones

“keystone of cranium”

Suture - Fibrous joint

Process - projection that contactsadjacent bone

Infant Skullcloses at 8 wks

closes at 9-18 mths

Fontanel – space between infant skull bones

Sinus CavitiesSinus: air-filled space

Compact & Spongy Bone

Compact Bonecanaliculi

Bone Classification

Long

IrregularShort

FlatArmsLegsPhalanges

WristAnkle

ScapulaSternumRibsSkull

VertebrateHipPatella

Anatomy of Long Bones

Anatomy of Short, Flat & Irregular Bones

Osteon Structural and functional unit of bone

• Haversion Canal– Allows passage of blood vessels, lymphatic vessels, and nerve

fibers• Lamella

– Concentric rings of collagen fibers around haversion canal– Allows bone to withstand force

• Lacunae– Small cavities occupied by osteocytes that join lamella

• Canaliculi– Hairlike canals that join lacunae to each other and the central

canal– Allow osteocytes to exchange nutrients, wastes, and chemical

signals via gap junctions

Type of Cells in Bone

• Osteoblast– Build bone cells– Synthesize and secrete organic components of bone matrix– Initiate calcification– Found in periosteum and endosteum

• Osteocytes– Mature bone cells– Formed when osteoblasts get trapped in matrix– Do not secrete matrix– Maintain bone tissue

• Osteoclasts– Bone resorption (digest/break down matrix): part of normal bone

growth, development, maintenance and repair– Found in endosteum

Bone Matrix

• Organic components (1/3)– Collagen fibers

• Provide resilience against stretching and twisting

• Inorganic components (2/3)– Mg, F, Na – Salts that interact to form hydroxyapatite

• Calcium phosphate• Calcium hydroxide

– Provide hardness and resist compression

Types of Tissue in Bone

• Connective– Osseous– Dense fibrous– Adipose– Vascular– Lymphatic

• Nervous

Bone Marrow• Red = hematopoietic tissue

– Bone cell forming tissue– Everywhere in infant

• Yellow = fatty tissue– Young to middle age develop

in shafts– Does NOT produce blood

I love anatomy!!!!!

Bone Development• Osteogenesis (ossification) – bone tissue

formation– Embryo: leads to skeleton

• Intramembranous ossification– Fibrous membrane replaced with bone

• Endochondral ossification– Hyaline cartilage replaced with bone– Most bones develop this way– More complicated (hyaline cartilage broken down first)

– Children: leads to bone growth– Adults: leads to bone remodeling and repair

Intramembranous Ossification

• Osteoblasts permit calcification• Some osteoblasts trapped in ossification

center (now considered osteocytes)• Growth is outward from ossification center• Osteoblasts require oxygen and nutrients,

so blood vessels are trapped in bone• Fibrous membranes→spongy bone→compact

bone• Outer fibrous membrane becomes periosteum

Endochondrial Ossification

• Chondrocytes in center of shaft increase in size and calcify

• Deprived of nutrients and die

• Vessels grow into perichondrium

• Inner layer turns to osteoblasts

• Perichondrium now periosteum

• Thin layer of bone formed around shaft

• Bone collar provides support

• Calcified cartilage breaks down

• Osteoblasts replace with spongy bone

• 1° oss. center- bone dev and spreads toward epiphysis

Endochondrial Ossification

• 1° oss. center enlarges

• Osteoclasts break down spongy bone

• Medullary cavity now open

• Osteoblasts move to epiphysis

Bone Growth

• Length– Primary ossification center

• center of diaphysis

• Thickness– Secondary ossification center

• center of epiphysis

Hormonal Effects on Bone Growth• Growth Hormone (GH)

– Produced by pituitary gland– Stimulates protein synthesis and cell growth

• Thyroxine– Produced by thyroid gland– Stimulates cell metabolism and increases osteoblast activity

• Sex Hormones at Puberty – Cause osteoblasts to produce bone faster than epiphyseal cartilage can divide

• Growth spurt• Epipyseal plate closure

– Estrogens (female)• Cause faster closure of plate than androgens

– Androgens (male)• Parathyroid Hormone

– Increases blood calcium level (decreases bone calcium)– Inhibits osteoblast; Stimulates osteoclast

• Calcitonin– “tones down” blood calcium level (increases bone calcium)– Inhibits osteoclast; stimulates osteoblast

Nutrients and Bone Growth

• Calcium and phosphate salts– Hormone calcitriol and Vit D allow absorption

• Vitamins A, C, K, B12

Types of Fractures• Simple - the bone is broken, but the skin is not lacerated• Compound - skin is pierced by the bone or by a blow that breaks the skin at

the time of the fracture• Greenstick - fracture on one side of the bone, causing a bend on the other

side of the bone.• Spiral – fracture wraps around bound in spiral manner• Comminuted - results in three or more bone fragments.• Transverse - fracture is at right angles to the long axis of the bone• Compression – occurs in vertebrate• Lisfranc - one or all of the metatarsal bones are displaced from the tarsus

Cervical Fracture

Compound Transverse Fracture

Lisfrank Fracture/Dislocation

(Fracture Hematoma)

Bony

Fractures

Skeletal Disorders• Osteomalacia

– “soft bones”– Lacking minerals (ie. Calcium, vit D)– Rickets

• Child form of osteomalacia• More detrimental since bones are still growing• Signs: bowed legs; deformities of pelvis, ribs and skull

• Osteomyelitis– “bone marrow inflammation”– Caused by pus-forming bacteria that enter via wound or nearby infection

• Osteoporosis– Bone degradation occurs faster than bone can be deposited– Decrease in bone mass– Porous bones– Fractures in the vertebrate and femur are common– Most common postmenopause: rapid decline in estrogen (stimulates

osteoblasts and inhibits osteoclasts

Skeletal Disorders

• Giantism– Childhood hypersecretion of GH– Excessive growth

• Osteogenesis Imperfecta– Osteogenesis imperfecta (OI) is a genetic disorder characterized by

bones that break easily, often from little or no apparent cause. There ae 9 different types.

• Pituitary Dwarfism– Childhood deficiency of GH– Short long bones; max height is 4 ft.

• Paget’s Neoplasms– Bone remodeling process disturbed– Bones are abnormal, enlarged, not as dense, brittle, and prone to

fracture – Affects older adults