Skeletal System 300 baby bones 206 adult bones

Skeletal System 300 baby bones 206 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 üBone 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 5 mph. 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 ü ü

Functions of Skeletal System • • • Support Protection Movement Hematopoiesis Reservoir for minerals and adipose tissue

Inner ear - 3 Skull – 22 bones Cranium – 8 Facial - 14 Vertebral Column - 32 Thorax - 27 Iliac crest 80 bones Upper limb – 30 Shoulder girdle - 2 Lower limb – 29 Pelvic girdle – 6 126 bones

Thoracic Cage 27 bones

Vertebral Column 32 bones

Abnormal Spinal Curvatures Lordosis Kyphosis Scoliosis

The Hand 27 bones

The Foot 26 bones

Arches of the Foot

The Skull 22 bones “keystone of cranium” Foramen – For nerves and vessels Ethmoid

Suture - Fibrous joint Process - projection that contacts adjacent bone

closes at 8 wks Infant Skull closes at 9 -18 mths Fontanel – space between infant skull bones

Sinus Cavities Sinus: air-filled space

Compact & Spongy Bone

Compact Bone canaliculi

Bone Classification Long Arms Legs Phalanges Short Wrist Ankle Flat Scapula Sternum Ribs Skull Irregular Vertebrate Hip Patella

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, B 12

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

Fractures Bony (Fracture Hematoma)

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