Bio 210 - Lecture HW 2 (6 Points) Name: Quiz and exam questions will emphasize material covered in lecture (and lab); use the textbook to clarify topics discussed in class. Below are questions that you should answer in detail and then use as a study guide. Questions emphasize concepts covered in class and are not meant to be specific examples of the questions that will be asked on tests. 1. What is cartilage? Define these terms – chondrocytes, lacunae, chondroblasts. What are the three types of cartilages, where are they located in the body, and what are the functions? What is articular cartilage? Cartilage: firm but flexible supporting connective tissue; avascular; no nerves, composed of gelatinous organic matrix; matrix contains collagen fibers (provides tensile strength) and a gel-like ground substance (provides flexibility and resilience); lubricating & weight bearing capabilities; found in developing skeleton & joints Chondroblasts: developing cartilage cells, actively secrete matrix during growth, then become chondrocytes; found in the inner cellular layer; young cells that turn into chondrocytes. Chondrocytes: mature cartilage cells that reside in cavities (pockets) called, lacunae. They are the only cells found in the cartilage matrix Lacunae: small chambers or cavities (pockets) that chondrocytes (mature cartilage cells) reside in. Three types of cartilage: 1. Hyaline Cartilage - has perichondrium - most abundant - has collagen fibers (not stain) - ground substance holds much water - stiff, flexible support Location: Articular cartilage = at joints (long bone) Costal cartilage = ribs/sternum Larynx + Trachea Function: - Provides firm attachment - Conducts pull of muscle - Reduces friction between muscle - Stabilizes relative positions of bones Surrounded by perichondrium (has two layers): 1. Outer fibrous layer- (dense irregular CT) mechanical support & protection 2. Inner cellular layer – growth and maintenance 2. Elastic Cartilage - skinny dark lines - has perichondrium - matrix has elastic fibers - tolerates repeated bending - does stain Location: Epiglottis = covers glottis when swallow Ears = Pinnae Function: - Stabilizes positions of vertebrae and penis - Cushions shocks - Permits expansion and contraction of organs 2. Fibro Cartilage - NO perichondrium - thick collagen fibers (arranged in rows) - resists strong compression and pulling forces - handles heavy weight - does stain Location: Vertebrae - Intervertebral discs Pubic bone - Pubic symphysis Knee - Menisci (plural) Function: - Provides strength to resist forces applied from many directions - Helps prevent overexpansion of organs such as urinary bladder 2. What are the functions of bones? What is the difference between red and yellow marrow and at what age do you see them? Where is red marrow located in adults? Know bone cell types, define: osteoblasts, osteoprogenitor cells, osteocytes, and osteoclasts. Where are osteoblasts and osteoclasts located specifically (two locations)? How do osteoblasts and osteoclasts remodel bone? Functions of bones (Osseous tissue): Support and protection of soft tissues: - Ribs protect the heart and lungs - Skull protects the brain - Vertebrae surround spinal cord Bones help our muscles move (leverage): - Muscles pull against attached bones (via tendons) we sit, stand, run, etc. Storage of minerals and lipids - Calcium and phosphate stored in bones - Energy reserves (fat) stored in yellow marrow Produce blood cells Red and Yellow Marrow: Bone Marrow: Loose connective tissue that may be dominated by yellow and red marrow. Found in the medullary (marrow) cavity. Energy reserves (fat) stored in yellow marrow (adipocytes) – found in medullary (marrow) cavity of adult long bones. (Note: Adults do have some red marrow, but the majority is yellow) In children, all skeleton has red marrow (mixture of mature and immature red and white blood cells and the stem cells that produce them) until they transition to yellow marrow, which starts at age 8-18. Bone Cell Types (4 Total): 1. Osteoblasts: Developing bone forming cells - Uptake calcium and phosphates from blood plasma, concentrates, forms insoluble crystals of hydroxyapatite = Ca10(PO4)6(OH)2 – makes bone hard, resists compression - Responsible for production of new bone (=osteogenesis) - Found in Endosteum: one cell thick, lines bone marrow cavity - Found in Periosteum: fibrous layer covers bone 2. Osteoprogenitor cells (Stem Cells): Found in inner periosteum and endosteum Differentiate from mesenchyme and produce daughter cells that become osteoblasts Important after bone fracture 3. 4. • • • • • Osteocytes: Mature bone cells, Spider shaped Once osteoblasts surrounded by matrix become osteocytes Bodies occupy small cavities (pockets) in solid matrix called lacunae ‘Spider legs’ occupy thin tubes called canaliculi (connect neighboring osteocytes, nutrients and wastes can diffuse) Maintain/monitor mineral content of surrounding matrix Osteoclasts: Bone degrading cells Giant cells with ruffled surface Found in endosteum and periosteum Release enzymes by exocytosis and dissolve hydroxyapatite. Ca 2+ and PO4 3- , ions enter bloodstream Bone erosion process = osteolysis Malnourished individuals would have high osteoclast activity How do osteoblasts and osteoclasts remodel bone? The remodeling cycle consists of three consecutive phases: 1. Resorption: osteoclasts digest old bone 2. Reversal: mononuclear cells appear on the bone surface 3. Formation: osteoblasts lay down new bone until the resorbed bone is completely replaced 3. How is bone like ‘fiberglass’? What is organic and inorganic components of bone, % of each, and function of each? How is bone like ‘fiberglass’? Hydroxyapatite = Glass Fibers Collagen Fibers = Plastic in which glass fibers embed Glass fibers in plastic – makes a tough, stress resistant material Like Hydroxyapatite in collagen fibers of bone What is organic and inorganic components of bone, % of each, and function of each? 35% Organic Component = Collagen fibers, proteins, cells Function: increases tensile strength, bone withstands stretching & twisting stresses 65% Inorganic Salts = Hydroxyapatite Function: makes bone hard, resists compression 4. Where is compact bone located? What other term means compact bone? What is an osteon? Know the structure of an osteon and its parts, define: lamellae, osteocytes, haversian canal, canaliculi, and Volkmann’s or perforating canals). Where is compact bone located? Compact bone is the solid, hard outside part of the bone What other term means compact bone? Outer Compact (or Cortical) Bone Osteons: many osteons = compact bone *replaced every 10 years What is an osteon? Know the structure of an osteon and its parts Osteon (or Haversian System): The basic functional unit of mature compact bone; Osteons are cylindrical structures that contain a mineral matrix and living osteocytes connected by canaliculi, which transport blood. They are aligned parallel to the long axis of the bone. Osteons parts: Lamellae (rings): layers of compact matrix that surround a central canal called the Haversian canal; Made up of collagen fibers; Provide strength; Gives some flexibility Osteocytes in Lacunae (pockets): maintain and monitor protein and mineral content of surrounding matrix Central or Haversian Canal: Contains blood vessels that supply the osteon, nourish osteocytes Canaliculi: (‘little canals’) Interconnect (the lacunae of an osteon) osteocytes with each other; Form branching network that reaches central canal; Route for diffusion of wastes and nutrients Perforating or Volkmann’s Canals: Blood vessels that connect central canals of different osteons to each other 5. Where is spongy bone located? What two other terms mean spongy bone? What is it made of? Why does it lack osteons? How do nutrients reach osteocytes in spongy and compact bone? What is the function of spongy bone? What are ligaments and tendons? What connective tissue type are tendons made of? Where is spongy bone located? Cancellous bone is found inside compact bone This is where bone marrow is found What two other terms mean spongy bone? Inner Spongy (Trabecular or Cancellous) Bone *replaced every 3-4 years What is it made of? Cancellous bone is made up of a mesh-like network of tiny pieces of bone called trabeculae (Lamellae form thin branching plates called Trabeculae) Why does it lack osteons? Because trabeculae do not have central canals or perforating canals. Trabeculae are thin enough to derive their nourishment from surrounding vessels. How do nutrients reach osteocytes in spongy and compact bone? Spongy bone: nutrients reach osteocytes by diffusing through the canaliculi from capillaries in the endosteum surrounding the trabeculae. Compact bone: nutrients travel from the blood supply of the medullary cavity through perforating (Volkmann's) canals that meet up with a central canal for each osteon. From a central canal, canaliculi connect with osteocytes. What is the function of spongy bone? Provides structural support and flexibility without the weight of compact bone What are ligaments and tendons? Ligaments: Connect bone-to-bone (help stabilize joints) Tendons: Connect muscle-to-bone (tough, but not very stretchy) What connective tissue type are tendons made of? Both tendons and ligaments are made up of dense regular connective tissue (fibrous tissue and collagen) *They are both poorly vascularized and contains no fat or defense cells 6. How do bone deposition and bone reabsorption rates change? How does the parathyroid gland (parathyroid hormone) and thyroid gland (calcitonin) influence bone? What are the results of those hormone secretions on bone and the body? How do bone deposition and bone reabsorption rates change? Environmental conditions, age/ hormones (bones of adolescents are much stronger than those of post-menopausal women), physical activity (increased muscular development will involve the remodeling of bones; increases bone strength; lays down more hydroxyapatite), nutrition (not getting enough nutrients and minerals such as calcium) How does the parathyroid gland (parathyroid hormone) and thyroid gland (calcitonin) influence bone? Parathyroid gland (located in the throat) Releases parathyroid hormone (PTH) Stimulates osteoclasts to resorb bone Releases calcium into blood PTH release occurs when blood calcium levels are low Thyroid gland (calcitonin) Releases calcitonin hormone, especially in children Inhibits osteoclasts (so children can lay down bone and grow) Increases rate of calcium loss in urine What are the results of those hormone secretions on bone and the body? These hormones control levels of calcium in the blood, energy levels, and the ability to grow.
