Skeletal System

Fun Facts 300 baby bones 206 adult bones Humans & giraffes have same # neck bones Smallest bone= inner ear (hammer, anvil, stirrup) Longest bone= femur >1/2 in hands & feet

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

80 bones 126 bones Skull – 25 bones Vertebral Cranium – 8 Column - 33 Facial - 14 Vertebral Column - 33 Inner ear - 3 Thorax - 27 Iliac crest 80 bones Upper limb – 30 Shoulder girdle - 2 Lower limb – 29 Pelvic girdle – 6 126 bones

https://www.youtube.com/watch?v=8W-2yT22l-k

Thoracic Cage 27 bones

Vertebral Column 33 bones 5 fused 4 fused

Abnormal Spinal Curvatures Lordosis Kyphosis Scoliosis

The Hand 27 bones

The Foot 26 bones

Arches of the Foot

The Skull 25 bones Foramen – For nerves “keystone of cranium” and vessels Ethmoid Ethmoid

Suture - Fibrous joint Process - projection that contacts adjacent bone

Infant Skull closes at 8 wks 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 Flat Long Short Irregular Scapula Arms Sternum Ribs Skull Arms Legs Phalanges Short Irregular Wrist Ankle 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 Osteocytes Osteoclasts 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) Inorganic components (2/3) 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 Nervous Osseous Dense fibrous Adipose Vascular Lymphatic Nervous

Bone Marrow Red = hematopoietic tissue Yellow = fatty 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!!!!! https://www.youtube.com/watch?v=rDGqkMHPDqE

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 https://www.youtube.com/watch?v=gh6J2CHR_q4

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 https://www.youtube.com/watch?v=RpV1t9ZMSxY

Bone Growth Length Thickness 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

Categories of Fractures Simple vs. Compound Simple (Closed) - the bone is broken, but the skin is not lacerated Compound (Open) - skin is pierced by the bone or by a blow that breaks the skin at the time of the fracture Stable vs Displaced Stable - fracture is barely out of place; broken ends are still aligned and stay in place while healing Displaced – broken ends are separated and do not line up; often requires surgery Displaced

Types of Fractures Spiral – fracture wraps around bound in spiral manner Comminuted - results in three or more bone fragments. Transverse - fracture is at right angles to the diaphysis Oblique – slanted fracture along the diaphysis

Types of Fractures cont. Greenstick - fracture on one side of the bone, causing a bend on the other side of the bone. Compression – occurs in vertebrate Lisfranc - one or all of the metatarsal bones are displaced from the tarsus Stress/Hairline - an overuse injury; the fatigued muscle transfers the overload of stress to the bone causing a tiny crack Impacted - one fragment is firmly driven into the other Compression Lisfranc

Fracture Repair Bony (Fracture Hematoma)

Skeletal Disorders Osteomalacia Osteomyelitis Osteoporosis “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 Acromegaly Pituitary Dwarfism Childhood hypersecretion of GH Excessive growth Acromegaly Adult hypersecretion of GH Overgrowth of face, feet, hands 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