Bio124 Chapter 6-9 Final Cartilage/Bone/Skeleton (PDF)

ssnakess.com Chapter 6: The Skeletal System (and some of 7 and 8) Does a whale have a neck? What kind of vertebra? Yes! Whale cervical vertebrae The Skeleton -Approximately 206 bones Appendicular vs Axial? The Skeletal System (bones are living)...

ssnakess.com Chapter 6: The Skeletal System (and some of 7 and 8) Does a whale have a neck? What kind of vertebra? Yes! Whale cervical vertebrae The Skeleton -Approximately 206 bones Appendicular vs Axial? The Skeletal System (bones are living) Includes the following: – Bones – Cartilage – Ligaments, tendons, cartilage and other supportive connective tissue Cartilage is a shock absorber and reduces bone damage Ligaments connect bones to bones Tendons connect bones to muscles Bones covered with periosteum Internally lined with endosteum (both CT)  Living Bone- Two main building blocks: 1. Inorganic mineral – Calcium Phosphate 2. Protein = Collagen (flexible) Bone is rigid but not brittle…Because of? – Flexible Collagen Bone after exposure to weak acid leaves Collagen fibers Bone matrix composition: Small plates of Ca3(PO4)2 lie alongside the collagen fibers (like cement with rebar)… Calcium Phosphate Crystals  What is the hardest matrix material? Tooth enamel! Cartilage & Bone Are Critical to Skeleton Function Cartilage Functions 1) Supporting soft tissues 2) Providing a gliding surface at articulations 3) Providing a model for formation of most bones Which cells produce cartilage matrix? Fibers? Which cells maintain cartilage matrix? Skeletal System Functions 1) Support & Lever Action (for movement) – Provides attachment sites for muscles – Scaffold or framework to support soft tissues 2) Protection – Skull protects? – Ribs Protect? – Vertebrae Protect? 3) Storage – Mineral homeostasis (Ca++ & PO4-) needed by all cells, especially muscle cells… – Lipids (yellow marrow) – Also - stem cells for cartilage, fat or bone cells) 4) Blood cell production (Hemopoeisis) – red bone marrow has blood stem cells, which produce (erythrocytes, leukocytes, and thrombocytes) Characteristics of cartilage & bone: Characteristics Cartilage Bone Mechanical Rigid but flexible Hard and strong Properties Mature Cell Name Chondrocytes Osteocytes Composition of Protein Protein + Ca3(PO4)2 Matrix Vascularization Avascular Vascular Nerve Innervation No Yes Growth/Repair Slow Fast Membrane Perichondrium Periosteum  Bones Classification Human bones are divided into four classes based on their shape.  Periosteum: Covers outer surface of bone except where articular cartilage is located. Made of Dense Irregular Connective Tissue. Has outer fibrous layer & inner cellular layer. Anchored to bone by Collagen Fibers known as Perforating Fibers. Endosteum: Incomplete layer of cells that covers all internal surfaces of bone. Contains Osteoprogenitor cells, osteoblasts, and osteoclasts. Types of Bone 1. Compact bone – Basic functional unit = osteon – Osteocytes (mature bone cells) arranged within concentric layers (lamellae) around central canal 2. Spongy bone – No osteons – Lamellae form trabeculae (rods or plates) that significantly reduce weight, but maintains strength femur Osteon Components – Compact Bone 1) Central canal – at center of osteon, contains blood vessels and nerves 2) Concentric lamellae – layers of compact bone that surround central canal Osteon Components 3) Osteocytes – mature bone cells 4) Lacunae – spaces that house osteocytes 5) Canaliculi – cytoplasmic extensions of osteocytes, allow communication between cells Other Components of Compact Bone 6) Perforating canals – connect central canals 7) Circumferential lamellae – layers of compact bone that surround outer periphery of bone 8) Interstitial lamellae – layers of compact bone that are remnants of old osteons A first look at bone formation Development of Bone  Overview Mesenchyme Stem cell Osteoprogenitor Osteoblast Chondroblast Fibroblast Osteocyte Chondrocyte Collagen Cartilage Bone  First some background Terminology: Mesenchyme – Star shaped cells- They are stem cells that give rise to all connective tissue. Osteoprogenitor From mesenchyme - (usually in endosteum & periosteum) Can divide & differentiate into osteoblasts Differentiate during bone formation and after bone fracture...  Background Terminology (continued): Need Fibers in Bone, so Mesenchyme can also give rise to fibers such as: Fibroblasts – Produce all connective tissue fibers collagen, reticular & elastic fibers Chondrocyt1HJk3 Chondroblasts – cartilage forming cells Chondrocytes- “encased” chondroblasts…  More terminology Osteoblast – bone forming cells. Secrete osteoid (uncalcified bone matrix) Differentiate into Osteocytes Osteocyte – “Encased” osteoblast Mature bone cells occupying lacunae (maintains bone) detect mechanical stress and communicate with osteoblasts Osteoclast – bone destroying cells (osteolysis) Giant, multinucleate (fused bone marrow stem cells) Contain lysosomes Secrete HCl Dissolve bone (release Ca+ & PO4-) Bone cells (review) What cell builds bone? – Osteoblast What cell produces osteoblasts? – Osteoprogenitor cells from Mesenchyme. What are mature bone cells called? – Osteocytes Where are osteocytes trapped? – Lacuna in an osteon What cell breaks down bone? – Osteoclast… Putting it all together… Bone formation- 2 forms 1. Intramembranous Ossification: Direct from – Mesenchyme to Osteocyte (Bone) – 10% bones (skull, clavicle, scapula, os coxa) 2. Endochondral Ossification: Indirect via cartilage… A.K.A. = Cartilage Replacement Bone Formation – Mesenchyme to Cartilage to Osteocyte (Bone) – Most Common (90%)  Intramembranous Ossification: “Direct” ossification (Forms bone sandwich) Osteoblasts form within connective tissue (“dermal bones”). Only about 10% of your bones form this way: many in the skull, clavicle, scapula, os coxae & all sesamoid bones (including patella). Name bones in skull that form this way…  Intramembranous Ossification (p. 154): Sequence of events: Step 1 – Mesenchyme cell clusters become osteoprogenitor cells that become osteoblasts. Osteoblasts produce osteoid (uncalcified bone matrix). This forms the ossification center… Increasing calcification More Intramembranous Ossification Step 2 – Bony trabeculae begin to radiate out from the ossification center. Blood vessels branch & grow. Step 3 – Over time, this bone assumes the structure of spongy bone with blood vessels among the trabeculae. Step 4- Bone remodeling by osteoclasts results in two layers of compact bone with spongy bone and small marrow cavities in between. A sandwich!... Endochondral Ossification 1) Fetal hyaline cartilage model develops from mesenchyme a) Some mesenchymal cells become chondroblasts, which secrete cartilage matrix b) Chondroblasts → chondrocytes c) Perichondrium forms around cartilage Endochondral Ossification 2) Cartilage calcifies, periosteal bone collar forms a) Chondrocyte hypertrophy, resorb cartilage matrix b) Matrix begins to calcify c) Chondrocytes die d) Blood vessels invade spaces e) Perichondrium becomes periosteum f) Osteoblasts secrete osteoid around diaphysis Hardens to form periosteal collar Endochondral Ossification 3) Primary ossification center forms in diaphysis a) Osteoid secreted onto remains of cartilage b) Bone development extends toward epiphyses c) Bone replaces calcified, degenerating cartilage Endochondral Ossification 4) Secondary ossification centers form in epiphyses ▪ Begins at birth, although some form later ▪ Same process as in diaphysis Also happening… ▪ Osteoclasts resorb some bone matrix in diaphysis ▪ Medullary cavity forms Endochondral Ossification 5) Cartilage remains only at articular cartilages and epiphyseal plates – Epiphyseal plate = growth plate Endochondral Ossification 6) Epiphyseal plates ossify – Form epiphyseal lines Age 10-25 Bone Male Age at Epiphyseal Union (years) – Growth stops Humerus, lateral epicondyle 11–16 (female: 9–13) Humerus, medial epicondyle 11–16 (female: 10–15) Humerus, head 14.5–23.5 Proximal radius 14–19 Distal radius 17–22 Distal fibula and tibia 14.5–19.5 Proximal tibia 15–22 Femur, head 14.5–23.5 Distal femur 14.5–21.5 Clavicle 19–30 Growth of Bone and Cartilage Two types of growth: 1) Interstitial growth – growth in length Occurs at epiphyseal plate in bone 2) Appositional growth – growth in diameter Epiphyseal Plate Morphology Zone 1 – small chondrocytes, resemble healthy hyaline cartilage, secures epiphysis to epiphyseal plate Zone 2 – rapid mitotic division of chondrocytes Zone 3 – chondrocytes cease dividing and begin to hypertrophy Zone 4 – only a few cells thick, calcification occurs here Zone 5 – new matrix of bone deposited on calcified cartilage matrix Bone Highly Vascularized  Summary of Endochondral Ossification Hyaline cartilage model develops (in fetus-chondroblasts). Cartilage calcifies and periosteal collar forms. Primary ossification center (osteoblasts) in diaphysis. (Blood) Secondary ossification centers (epiphysis)-(increased blood) Replacement of cart. w/ bone (except..EP & AC). Bone reshaped. When Growth stops - Complete ossification (plate ->line) This slide simply shows epiphyseal plates in a juvenile and all the extra cartilage in the wrist, etc.! juvenile adult Photo of human fetus skeleton Diameter = Appositional growth New bone is produced on the bone’s exterior. New osteons will organize. Osteoclasts on the endostium will dissolve bone enlarging the marrow cavity…  Bone Growth: Influencing Factors: Stress or Force (e.g., exercise) Hormones: Calcitonin from the Thyroid gland & Parathyroid Hormone from the Parathyroid Bone! glands control homeostasis of Ca++ Where does the Ca++ come from or go to? Vitamin A – activates osteoblasts Vitamin C – promotes collagen production Vitamin D – promotes absorption of calcium and phosphate into bone Timing of Hormone Control of Bone Growth Preadolescence – Growth hormone and thyroid hormone stimulate bone growth Early Adolescence – Estrogen and testosterone stimulate bone growth Late Adolescence – Estrogen and testosterone cause replacement of cartilage growth plates with bone Epiphyseal plates (EP) close – growth stops Bone Growth and Development After EP closure, osteoclasts and osteoblasts remain active – Activities normally balanced High turnover rate – In young adults – 1/5th of skeleton recycled and replaced each year – Why? because of bone remodeling Bone Remodeling Some parts of bone constantly remodeled – Helps maintain calcium and phosphate levels Examples of differences – Spongy bone in head of femur May be replaced 2-3 times a year – Compact bone of shaft Remains largely untouched Bones and Physical Stress Heavily stressed bones – Become thicker and stronger – Develop more pronounced surface ridges Lack of ordinary stress – Bones become thin and brittle _____ _____ is important for maintaining bone structure  NASA's Boeing Crew Flight Test astronauts Butch Wilmore & Suni Williams. Photo: SKyNews/NASA/AP Muscle contraction and gravitational forces – Increase osteoblast activity Effects of – Increase bone density Exercise on Lack of weight-bearing exercise (DUILI) Bone – Stimulates osteoclasts – Decreases bone density – Think about bedridden patients or astronauts Bone Degeneration Can occur after brief periods of inactivity – *Ex. Using crutches After a few weeks – unstressed leg loses 1/3 of bone mass Quickly rebuilds upon normal weight and use*  Cartilage: Structure Make-up Cartilage is made of cells called chondrocytes which become impeded in a matrix of thick gel. – This is the final form of Cartilage! Cartilage begins its journey as cells called chondroblasts that produce the thick gel matrix. – Chondrocytes are what chondroblasts become after they become trapped in the matrix they produce. The spaces the chondrocytes occupy in the matrix are called lacunae (just like bone) Mature cartilage is avascular.  Cartilage: Growth Patterns Cartilage has two distinct growth patters: – Interstitial Growth = Internal Growth Growth within the cartilage itself (mitosis of chrondrocytes). – Appositional Growth = External Growth Peripheral and surface growth of the cartilage (mitosis of mesenchyme and chondroblasts) Cartilage Developmental Growth Both types of growth during embryonic growth. Interstitial growth stops as cartilage matures Cartilage grows laterally via Appositional growth. Fully mature cartilage has no growth, except after injury, but limited regrowth. Bone and Aging Major changes: Decreased collagen production Less Ca2+ and other bone salts – Weaker, decreased density/mass Can result in osteoporosis – Brittle bones – Fracture easily Osteopenia Inadequate ossification – Thinning/weakening a normal part of aging – Begins between ages 30 and 40 Osteoblast activity declines Osteoclast activity continues Not all bone equally affected – Epiphyses, vertebrae, and jaws lose more Results in fragile limbs, loss of height and loss of teeth Osteopenia Note: Bone density peaks in early adulthood Men vs Women – Women ~ 8% loss per decade – Men ~ 3% loss per decade Osteopenia vs Osteoporosis Over 45 – ~ 29% of women and ~ 18% of men have osteoporosis – Women have decline in estrogen after menopause which accelerates condition www.algaecal.com Osteoporosis Osteoporotic bone Normal bone Bone Fractures Causes of Fractures – Stress – Pathology – Trauma Simple (closed) vs Compound (open) Bone Fractures & Repair (text p.163-164): Fracture types: General types: Simple Compound Complete Incomplete (Closed) (Open) A. Fracture types: Specific types: Greenstick Comminuted Transverse Spiral (type of incomplete) Oblique A look at some X-rays Broken head of the humerus. External heart monitor tab. Female in mid 80’s. Same female as in last slide with repair. Metal and screws. Patient died a few weeks later. Horseback riding. 13 year old girl. Arm wrestling with non- dominant arm! 20 year old male. Same male as in last slide with repair. Dislocated finger joint. X-ray discovered sesamoid bone! Female in mid 30’s. X-rayed for injured toe. Discovery of sesamoid bones. Female in mid 30’s. X-rayed for pain under toes. Discovery of sesamoid fracture. Female early 20’s. Stress fracture due to ballet. X-rayed for injured foot. Broken metatarsal bones. Female in mid 20’s. Male in mid 70’s, jogging. Broken metatarsal bones. Female in early 60’s, walking. Left ankle inversion. Broken proximal, metatarsal process. Male, early 20s, fell while hiking at Bishops peak 4 surgeries needed X-rayed for repaired ankle. Broken lateral maleolus. Male in early 20’s. X-rayed for repaired finger. Broken phalanges. Female in early 20’s.  What bone is this? Femur Male, 39, With Duchenne Muscular Dystrophy. Broken during transfer from bed to chair.  X-rayed for injured leg. Injured distal tibia. Not seen in this view. Male 1.5 years. Notice lack of patella (normal) and all the cartilage in foot and epiphyses. Same patient as last x-ray showing hips. Male 1.5 years. Notice the separate bones of the os coxae. X-rayed for injured back. Female (16 years) playing softball just before x-ray. Standard question asked by tech: “Are you pregnant?”. Answer: “No!” Patient gave birth one hour later! Notice cranium of baby engaged into birth canal!!! Bone Fracture Healing 1) Fracture hematoma (blood clot) forms (4-8 hours) a) Broken blood vessels leak blood b) Blood clots form fracture hematoma 2) Fibrocartilaginous (soft) callus forms (2-7 days) a) Chondrocytes secrete fibrocartilaginous matrix b) Osteocytes secrete Osteoid c) Ends of fracture united by matrix Bone Fracture Healing 3) Bony (hard) callus replaces soft callus via endochondral ossification (~ 2+ weeks) a) New osteoblasts produce trabeculae of primary bone b) Grows and thickens for several months 4) Bone is remodeled (after 2+months to years) a) Compact bone replaces spongy bone at outer margins b) Remodeling occurs in response to strain  A. B. https://www.rch.org.au/fracture-education/fracture_healing/ A. These are sequential radiographs of a child who sustained a fracture of midshaft of rt. humerus during birth. Note very rapid healing w/ extensive callus by day 7 & remodeling. B. These sequential radiographs of a 14 month child who sustained a fracture of midshaft of right femur. Again, note the rapid healing w/ extensive callus by day 18. While You Are Studying… What is ossification? What are the two types of ossification? – Describe each of these processes: Type of bones in which ossification occurs Type of tissue in which ossification centers form Number of ossification centers Steps involved What are the two types of bone growth? – Which type occurs throughout life? While You Are Studying… What are the functions of cartilage? What types of growth are seen in cartilage? What are the functions of the four types of bone cells? Describe the microscopic anatomy of compact bone Draw the microscopic anatomy of compact bone Describe the microscopic anatomy of spongy bone Compare and contrast compact vs spongy bone While You Are Studying… How does bone density change throughout life? Describe the factors that affect bone homeostasis Describe the epiphyseal plate morphology Describe the process of bone fracture healing Describe the effects of aging on bone Compare and contrast osteopenia and osteoporosis Know about the paranasal sinuses, orbital complex, bones associated with the skull, the ribs, the pelvis, the vertebral column, the arches, and the fetal skull  We will finish the remaining slides next week Paranasal Sinuses Air-filled spaces around nasal cavity – Mucous lining humidifies and warms inhaled air – Lightens skull – Resonant chambers for sound production when speaking Paranasal Sinuses The Orbital Complex Orbits – bony cavities in skull – Hold and protect eyes – Consist of multiple bones – Contain muscles that move eyes Bones Associated with the Skull Auditory ossicles: Three tiny bones in each temporal bone – important in hearing: 1. Malleus 2. Incus 3. Stapes Bones Associated with the Skull Hyoid bone: Located between mandible and larynx – Does not articulate with another bone – Attachment site for tongue and muscles of larynx – used in swallowing Fetal Skull Infant cranial bones connected by flexible areas of dense regular connective tissue – fontanelles – Major fontanelles: Mastoid Sphenoidal Posterior Anterior Vertebral Column 26 bones – 24 individual vertebrae Cervical: 7 bones Thoracic: 12 bones Lumbar: 5 bones – Two inferior bones (fusions of several vertebrae) Sacrum: 5 fused vertebrae Coccyx: 4 fused vertebrae Ribs 12 pairs – Articulate posteriorly with thoracic vertebrae – True ribs: Ribs 1–7; articulate anteriorly with sternum via costal cartilages – False ribs: Ribs 8–12; costal cartilages do not attach directly to sternum Floating ribs: False ribs 11 and 12 – do not articulate with sternum Pelvis Most reliable indicator of sex of a skeleton – Because of requirements of pregnancy and childbirth Major differences: – Female ilia laterally flared = wider pelvis – Pelvic inlet Female = wide oval Male = heart-shaped – Female subpubic angle is wider: Greater than 100° compared to less than 90° in males – Greater sciatic notch wider in female Arches of the Foot Help prevent pinching of muscles, nerves, and blood vessels Three major arches: – Medial: From heel to hallux; highest arch – Lateral: From heel to fifth toe; lowest arch – Transverse: Perpendicular to other arches; along distal row of tarsals