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Exam #1 wrap-up Scores on Exam #1, 10-15-14 Answer key and scores are posted to Canvas. # of students 12 10 8 6 4 2 0 <70 70-79 80-89 90-100 The 2 questions for which scores were the lowest: In which kind of connective tissue can you normally see a mix of cells that do and do not have nuclei? a. Connective tissue proper b. Fluid connective tissue YES c. Hyaline cartilage d. Supporting connective tissue Which kind of connective tissue is a major component of the walls of large arteries? a. dense irregular b. dense regular c. elastic d. smooth muscle YES Remember: BIOL 241 covers these 1st 4 organ systems. Integumentary: Ch. 5. Skeletal: Ch. 6-9. Muscular: Ch. 10-11. Nervous: Ch. 12-16. (Spotlight Figure 1-1) Chapter 6 Osseous Tissue and Bone Structure Lecture Presentation by Lee Ann Frederick University of Texas at Arlington (heavily modified by GJC) © 2015 Pearson Education, Inc. An Introduction to the Skeletal System • The Skeletal System • What does it include? bones of the skeleton; cartilages, ligaments, and other connective tissues. Our main focus: bones! © 2015 Pearson Education, Inc. 6-1 Functions of the Skeletal System • Five Primary Functions of the Skeletal System * Support * Storage of Minerals (calcium) and Lipids (yellow marrow) * Blood Cell Production (red marrow) * Protection * Levers for muscles (allow movement) [Cartilage : protects adjacent bones] © 2015 Pearson Education, Inc. Bone Shapes What do you normally picture when you think of a bone? The kind a dog chews on? This is a “long bone,” one of four basic bone shapes. The others are: short, flat, and irregular. (Lab manual considers sesamoid and sutural to be examples of irregular bones, so we will follow that system as well.) Bone Shapes: Long vs. Flat Spongy bone Epiphysis Metaphysis Note: both types have spongy and compact bone, but in different places! Language notes: epi = outer, meta = middle, medulla = middle/center Compact bone Diaphysis (shaft) Medullary cavity Metaphysis Epiphysis Compact bone (Cortex) Spongy bone (Diploë) Metaphysis – where bones grow! (Details to come…) Figure 6-3 Bone Structure. Tricky bones, example 1: wrist/hand Finger bones – metacarpals and phalanges – aren’t really that long, but have the basic shape of “Long” bones and are classified as long. It’s the carpals that are classified as short bones. Short bones have a different, “box-like” shape. Figure 6-1c Tricky bones, example 2: parietal bone; ribs Both of these are considered FLAT bones. Bone Markings – see Table 8.1 of lab manual Projections/Processes/Elevations vs. Depressions/Openings/Tunnels 1. You don’t need to memorize these general terms, but be aware and use as a guide when looking at specific bones. Projections for tendon or ligament attachment: crest, epicondyle, line, process, spine, trochanter tubercle, tuberosity 2. Projections for forming joints: condyle, facet, head, ramus 3. Depressions/openings for blood vessels/nerves: fissure, foramen, groove, notch 4. Other depressions/openings: fossa, meatus, sinus Variations in bone shapes and markings offer clues about a person’s life! (next slide) Anthropologists & pathologists analyze bones http://anthropology.si.edu/writteninbone/ LEFT: Burned body found in fire. RIGHT: Part of baby skull, 17thcentury Maryland. LEFT: Was the fire the cause of death? Orange marks show broken ribs…. No signs of healing….. Wounds were made by long knife, so building was torched to hide a murder! RIGHT: baby with holes in skull. Any idea what happened here? Inadequate nutrition. Answer key and scores are posted to Canvas. Number of students Lab Quiz #1 wrap-up Scores on Lab Quiz #1 (out of 75) 10 8 6 4 2 0 51-57 60-66 69-75 Bone (Osseous) Tissue: semi-review Cells: (b) and (c) are COMPACT BONE Extracellular Matrix: vein nerve artery Canaliculus (i) Lacuna (ae) with osteocytes Lamella (ae) Central canal (contains nerves, blood vessels) Trabeculae of spongy bone lab manual, Figure 8.4; textbook, Figure 6-7 All of these concentric circles = 1 osteon Structure of a Long Bone • Diaphysis (dye-AFF-ih-sis) • The shaft • A heavy wall of compact bone, or dense bone • A central space called medullary cavity • Epiphysis (ee-PIFF-ih-sis) • Wide part at each end • Articulation with other bones (connections/joints) • Mostly spongy bone • Covered with compact bone (cortex) Cortex = “outside” vs. Medulla = “middle” © 2015 Pearson Education, Inc. Figure 6-3 Bone Structure. To which forces are long bones most vulnerable? Most vulnerable to “sideways” forces e.g., side tackle in football How do bones develop and mature? • “Endochondral Ossification” (for long bones, etc. - “inside cartilage turning to bone”) • Ossifies bones that originate as hyaline cartilage • Most bones originate as hyaline cartilage • There are several steps in endochondral ossification (next slides) © 2015 Pearson Education, Inc. Figure 6-11 Endochondral Ossification 1 1 Fetal bone: Hyaline cartilage, chondrocyte s in middle © 2015 Pearson Education, Inc. 2 Invasion of blood vessels; bring fibroblasts to become osteoblasts. 3 4 Hollowing out of center of bone (medulla); chondrocytes are dying off and migrating toward epiphyses. Figure 6-11 Endochondral Ossification (continued) 5 Hyaline cartilage on end 7 6 5 Epiphyses: spongy bone replaces hyaline cartilage. Blood vessels into epiphyses; spongy bone starts forming there as well. © 2015 Pearson Education, Inc. Post-puberty: epiphyseal plate (cartilage replaced with spongy bone) Lab manual figure: 8.5: Sequential migration of chondrocytes and osteocytes Bone Formation and Growth • Epiphyseal Cartilage (in diaphysis, migrating toward epiphysis) • When long bone stops growing, after puberty: • What happens to epiphyseal cartilage? • Converted to bone (by trailing osteocytes) • What’s visible on x-rays? (see next slide) © 2015 Pearson Education, Inc. Figure 6-10 Bone Growth at an Epiphyseal Cartilage. Post-puberty: epiphyseal cartilage (in metaphysis) has disappeared, leaving only thin epiphyseal plate (not visible here) © 2015 Pearson Education, Inc. End-of-chapter review question #29 Frank does not begin puberty until he is 16. What effect would you predict this will have on his stature? (a) Frank will probably be taller than if he had started puberty earlier – YES! (more time til end of puberty stops bone growth) (b) Frank will probably be shorter than if he had started puberty earlier (c) Frank will probably be a dwarf (d) Frank will have bones that are heavier than normal (e) The late onset of puberty will have no effect on Frank’s stature © 2015 Pearson Education, Inc. Bone Remodeling • Process of Remodeling • The adult skeleton: • Replaces mineral reserves • Recycles and renews bone matrix • Involves 3 cell types: • Osteoclasts: “tear up” bone tissue • Osteoblasts: build up bone tissue • Osteocytes: “mature” bone cells in lacunae, which maintain matrix © 2015 Pearson Education, Inc. Bone Remodeling Shin & Cho, Journal of Korean Society of Endocrinology 2005 Both happen simultaneously!!! Bone Remodeling • Process of Remodeling • Bone continually remodels, recycles, and replaces • What happens if deposition (by osteoblasts) is greater than removal? • Bones get bigger, stronger – sometimes TOO big (bone spur) • What happens if removal is faster than replacement? • Bones get thinner, weaker Exercise: weight-bearing exercise (support body weight), weight-lifting stimulates thickening of bones © 2015 Pearson Education, Inc. Bone remodeling & exercise: “Use it or lose it!” • Bed rest or “couch potato” behavior • Exercise (are all forms equally good?) J.F. Nichols et al., Osteoporosis International 2003 Old cyclists: lots of lowimpact exercise does not protect bones from thinning! Advice: mix it up, do some running/weight lifting! + NUTRITION (Ca, Phosphorus, D3 intake) (old) What would you recommend to maintain optimal bone density? (see previous slide) Variety: reach different bones and different muscles with different exercises! Bones, Hormones, and Nutrition • Normal Bone Growth and Maintenance Depend on Nutritional and Hormonal Factors • The hormone calcitriol • Made where? Kidney! • Helps digestive tract absorb what? • calcium • Synthesis requires what precursor? • Cholecalciferol (made in skin) • Liver continues conversion process © 2015 Pearson Education, Inc. Bones & Hormones • Osteoblast activity and synthesis of bone matrix is stimulated by hormones like growth hormone and estrogens/androgens. • Implications for anorexic teenagers? • Not enough nutrients, not growing bones well… Very hard to build this bone later (as an adult)! • Implications for older folks? • Less exercise … estrogen goes way down in postmenopausal women… (estrogen can be an issue in anorexic women as well!) 6-8 Calcium Homeostasis • The Skeleton as a Calcium Reserve • Bones store calcium and other minerals • Calcium ions are vital to: • Neurons • ions involved in electrical signaling; calcium specifically triggers neurotransmitter release at axon terminus • Muscle cells, especially heart cells • Calcium stimulates actin and myosin to interact => contract © 2015 Pearson Education, Inc. Calcium Homeostasis • Calcium ions in body fluids must be closely regulated • Homeostasis is maintained by 2 (or 3) hormones: calcitriol PTH = parathyroid hormone calcitonin * Intestinal absorption * Osteoclast activity increases blood calcium levels; Osteoblast activity decreases blood calcium levels * Kidney can retain calcium (or let it leave in urine) © 2015 Pearson Education, Inc. Figure 6-15a Factors That Alter the Concentration of Calcium Ions in Blood. a Factors That Increase Blood Calcium Levels Low Calcium Ion Levels in Blood (below 8.5 mg/dL) Parathyroid Gland Response Low calcium levels cause the parathyroid glands to secrete parathyroid hormone (PTH). PTH Bone Response Osteoclasts stimulated to release stored calcium ions from bone Intestinal Response Rate of intestinal absorption of calcium increases Kidney Response Kidneys retain calcium ions more calcitriol Calcium released Calcium absorbed quickly Ca2+ levels in blood increase © 2015 Pearson Education, Inc. Calcium conserved Decreased calcium loss in urine Figure 6-15b Factors That Alter the Concentration of Calcium Ions in Blood. b Factors That Decrease Blood Calcium Levels High Calcium Ion Levels in Blood (above 11 mg/dL) Thyroid Gland Response Parafollicular cells (C cells) in the thyroid gland secrete calcitonin. Calcitonin Bone Response Intestinal Response Osteoclasts inhibited while osteoblasts continue to lock calcium ions in bone matrix Rate of intestinal absorption of calcium decreases Kidney Response Kidneys allow calcium loss less calcitriol Calcium absorbed slowly Calcium excreted Calcium stored Ca2+ levels in blood decrease © 2015 Pearson Education, Inc. Increased calcium loss in urine Figure 6-15 set to music (revised) When blood calcium is HIGH, The thyroid sends out calcitonin; When blood calcium is LOW, The parathyroid gland gets goin’. When blood calcium is HIGH, There’s less intestinal absorption; When blood calcium is LOW, The kidney saves a greater portion. Figure 6-15 set to music (revised) Melody playback: http://www.noteflight.com/scores/view/0cbd7455cee28fb56162b76aef5256602dd2c6ee Summary of homeostasis in preceding figure • Regulated variable? • Blood calcium levels • Setpoint? • 8.5 to 11 mg/dL is apparently optimal • Effectors? • For high calcium: Thyroid? Calcitonin? Kidney, intestine, osteoclasts/blasts? (all of above) © 2015 Pearson Education, Inc. Fractures • Fractures • Cracks or breaks in bones • Caused by physical stress • Fractures are repaired in four steps 1. Bleeding 2. Cells of the endosteum and periosteum 1. Endosteum = “inner cells” at edge of medulla 2. Periosteum = cells on outside 3. Osteoblasts 4. Osteoblasts and osteocytes remodel the fracture for up to a year © 2015 Pearson Education, Inc. Figure 6-16 Types of Fractures and Steps in Repair. Spongy bone of internal callus Cartilage of external callus Fracture hematoma External callus Dead bone Bone fragments 1 Fracture hematoma formation. Spongy bone of external callus Periosteum Internal callus 2 Callus formation. External callus 3 Spongy bone formation. 4 Compact bone formation. Compare & contrast with inflammation! Inflammation Bone Fracture “First responder” cells Mast cells (release histamine) No great equivalent… Initial response Clot/scab with fibrin protein Clot/scab with fibrin protein Later rebuilding Collagen, mostly Cartilage & spongy bone “Good as new”? Not really – scar tissue Can be – extra-strong, but callus may intrude at joints © 2015 Pearson Education, Inc. Textbook Topic Lab Manual Chapter 7 The Axial Skeleton Exercise 9 Chapter 8 The Appendicular Exercise 10 Skeleton For these chapters we will not use the textbook, except as a backup resource. © 2015 Pearson Education, Inc.