BIOL 2401 EXAM 3 SF STUDY Q

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Dec 6, 2023

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BIOL 2401 Skeletal System, Articulations and Muscle Physiology Exam 3 Study Questions 1. List the components of the skeletal system. The components include bones, cartilage, ligaments and other CT that stabilizes or connects bones. 2. Compare and contrast compact and spongy bone. COMPACT is dense, rigid that’s white, smooth and solid. It makes up 80% of total bone mass. SPONGY is inside the compact bone and is porous. It makes up 20%. Spongy is also called cancellous/trabecular bone (think trab meshwork pattern) 3. Describe the 3 types and locations of cartilage within the skeletal system. HYALINE-Glass look, more space out, less fibers more ground. Location: attaches ribs to sternum, covers the ends of some bones (articular cart) and is the epiphyseal plates which is the cart within growth plates. FIBROCARTILAGE-Denser, fibers in same direction. Weight bearing kind that withstands compression. Location: Intervertebral discs, pubic symphysis (between pelvis) and menisci (cart pads of knee joints) ELASTIC-Busy, fibers going in all directions. Located in ears. 4. Explain the general functions of bone. •Support & Protect • Levers for Movement • Hematopoiesis (RBC production) •Storage of Mineral & Energy Reserves (minerals like calcium/phosphate) Calcium is an electrolyte. It helps w/ muscle contraction, blood clotting. Phosphate is important to plasma membrane. 5. Compare and contrast the four major classes of bones as determined by shape. LONG-Found in upper and lower limbs, fingers and toes. Longer than are wide. They have an elongated diaphysis (shaft). SHORT-Wrist bones, ankle bone, patella (knee cap) which is the largest sesamoid bone. FLAT-Roof of skull, shoulder blades, sternum and the ribs. Provide muscle attachment and protect underling soft tissues. IRREGULAR-Vertebrae, hip bones (ossa coxae) and several skull bones like ethmoid, sphenoid, maxilla. Have elaborate, complex shapes that do not fit the other categories.

6. Describe the structural components of a long bone. DIAPHYSIS-the shaft, elongated, cylinder shape that provides leverage and major weight support. Consists of compact bone with spongy bone internally. MEDULLARY-the hollow cavity within the diaphysis. In kids, this cavity contains red blood marrow, later replaced with yellow bone marrow in adults. EPIPHYSIS is the knobby end of a long bone. It can be proximal or distal. It has a thing outer layer of compact bone and more extensive spongy bone on the inside. Covering the joint surface of epiphysis is a thin layer of hyaline called articular cartilage that helps reduce friction and absorb shock in joints. METAPHYSIS is where the long bone widens and transfers force between DIA and EPIP. In a growing bone this area contains EPIPHYSEAL PLATE which is a thin layer of hyaline that helps with the length growing of the bone. In adults the remnant of this is called the EPIPHYSEAL LINE. 7. Compare the gross anatomy of other bones to that of a long bone. It is greater in length than width, has elongated, cylindrical shaft (diaphysis), it’s the most common bone shape. Located in upper and lower limbs like the arm, forearm, thigh, legs, toes and fingers. It varies in size. 8. Explain the general function of blood vessels and nerves that serve a bone. Bone is highly vascularized especially in spongy area. Blood vessels supply nutrients and oxygen required by cells and remove waste products from bone cells. One nutrient artery enters in and one exits out of the bone thru a small hole in the bone called a nutrient foramen. Vessels also include areas of the periosteum, endosteum and marrow cavity. 9. Compare and contrast the structure and location of the two types of bone marrow. 2 types: red bone marrow and yellow bone marrow. RED MARROW (myeloid tissue) contains reticular CT, developing blood cells and adipocytes. Found in children. Primary function is forming the blood cells of the body. Located in spongy bone. YELLOW MARROW has a fatty-appearing substance. RED produces blood cells, YELLOW stores energy as fat 10. Name the four types of bone cells and their functions. The 4 types are osteoprogenitor cells, osteoblasts, osteocytes and osteoclasts. •OSTEOPROGENITOR are the stem cells derived from mesenchyme aka embryonic connective tissue. They develop into osteoblasts. •OSTEOBLASTS are formed from progenitor stem cells and are the cells that form new bone. They synthesize and secrete an organic form of bone matrix called Osteoid. They build cells and are the bone makers. Some differentiate into osteocytes.

•OSTEOCYTES are cells inside the bone, they come from osteoblasts. The osteocytes get surrounded by new bone. They send out long branches that connect to other osteocytes. They can sense pressure or cracks in the bone and will direct where osteoclasts will dissolve the bone. •OSTEOCLASTS are large, multinuclear, phagocytic cells. They are the renovators and bone breakers. They’re come from the bone marrow. Involved in breaking down bone in a process called resorption. 11. Describe bone matrix composition, formation, and resorption. The matrix of bone has organic and inorganic components. The organic part includes osteoid which is produced by osteoblasts. Osteoid has a collagen and semisolid ground substance of proteoglycans, glycoproteins that suspend and support the collagen fibers. The organic parts given bone it’s tensile strength by resisting stretching, twisting and help w/ overall flexibility. The formation of bone starts when osteoblasts secrete osteoid. The entire process of bone forming requires a number of substances like Vit D and Vit C, also calcium and phosphate for calcification. Calcification is mineralization. It occurs subsequent to the osteoid when hydroxyapatite crystals deposit in the bone matrix. Bone resorption is a process where bone matrix is destroyed by substances released from osteoclasts into the extracellular space adjacent to the bone. 12. Compare and contrast the microscopic structure of compact bone and spongy bone. The structures consist of osteons and the osteons themselves have several components like central canal, concentric lamellae, osteocytes, lacunae, canaliculi, perforating canals, circumferential lamelle and interstitial lamellae.

13. Identify and describe the components of hyaline cartilage. It looks like a glassy matrix, gel like ground substance. More ground than fibers. Contains chondrocytes in their small spaces called lacunae. Hyaline is covered by a dense irreg CT called perichondrium which helps maintain it’s shape. Hyaline is avascular and no calcium present in matrix. 14. Compare interstitial and appositional growth of cartilage. Cartilage can grow both in length thru the process of interstitial growth and in width by appositional growth. Cartilage development begins during embryonic development. Later growth only occurs at periphery so it’s appositional. Once cart is fully mature, new growth stops. INTERSTITIAL is an increase in LENGTH that occurs within the inside regions of the cartilage in four steps. APPOSITIONAL is an increase in WIDTH along the cartilage outside edge in three steps.

15. List the bones that are produced by intramembranous ossification. It produces the flat bones of the skull, some facial bones, the mandible and the central part of the clavicle. It begins when the mesenchyme (embryonic CT) becomes thickened and condensed with a dense supply of blood capillaries and continues in the four main steps on the next question. 16. Explain the four main steps in intramembranous ossification. 1) Ossification centers form within thickened regions of mesenchyme beginning at week 8 of development. 2) Osteoid undergoes calcification. 3) Woven bone and its surrounding periosteum form. 4) Lamellar bone replaces woven bone as compact and spongy bone form. 17. List the bones produced by endochondral ossification. Endo (within) Chondral (cartilage) Ossification starts with hyaline cart and produces most of the bones of the skeleton including upper/lower limbs, pelvis, vertebrae and ends of the clavicle. 18. Explain the steps in endochondral ossification of a long bone. 1) Fetal hyaline cartilage develops 2) Cartilage calcifies and a periosteal bone collar form. 3) The primary ossification center forms in the diaphysis. 4) Secondary ossification centers form in the epiphyses. 5) Bone replaces almost all cartilage, except the articular cartilage and epiphyseal cartilage. 6) Lengthwise growth continues until the epiphyseal plates ossify and form epiphyseal lines. 19. Compare and contrast the five zones of the epiphyseal plate, and describe how growth in length occurs there. The 5 zones are continuous from the first zone nearest the epiphysis to the last zone nearest the diaphysis. 1) ZONE OF RESTING CARTILAGE-farthest from the medullary cavity and nearest the epiphysis. Has small chondrocytes throughout the cartilage matrix. This region secures the epiphysis to the epiphyseal plate. 2) ZONE OF PROLIFERATING CARTILAGE-Chondrocytes in this zone undergo rapid mitotic cell division, enlarge slightly and become aligned within lacunae. 3) ZONE OF HYPERTROPHIC CARTILAGE-Chondrocytes stops dividing and grow in size. Lacunae walls become thin because the chondrocytes resorb matrix as they grow. 4) ZONE OF CALCIFIED CARTILAGE-This zone has 2-3 layers of chondrocytes. Minerals are put in the matrix between the columns of lacunae. 5) ZONE OF OSSIFICATION-The walls breaks down between lacunae in the

columns and form long channels. The spaces of the channels are invaded by capillaries and osteoprogenitor cells from the medullary cavity. 20. Describe the steps of appositional growth. AP growth occurs within the periosteum which is the sheath outside your bones that supplies them with blood, nerves and cells that help them grow and heal. In the process the osteoblasts produce and deposit bone matrix within layers. Like tree rings, called external circumferential lamellae. As they increase in number the structure increases in diameter so the bone becomes wider with the new bone being laid down at the periphery. AP growth continues thru adults lifetime. 21. Describe bone remodeling, and explain how this remodeling is affected by mechanical stress on bone. Bone remodeling is the process of continually adding new bone and removing old bone. Even when bones become adult sized, they bone continues to renew and reshape itself throughout a person’s lifetime. Mechanical stress happens in the form of weight bearing movement and weight bearing exercise. Osteocytes will detect this stress and tell the osteoblasts. The osteoblasts will then increase the production of osteoid which is followed by a deposit of mineral salts. Certain weight bearing movements will help increase bone mass like weight training, walking, running, jumping but things like elliptical, swimming, cycling have less of an positive effect because they’re not weight bearing. 22. List the hormones that influence bone growth and bone remodeling, and describe their effects. Hormones are molecules released from one cell into the blood and are transported thru the body at affect other cells. The hormones that can have an effect are: PROMOTES BONE GROWTH •Growth Hormone-stimulates liver to produce hormone IGF •Thyroid Hormone-stimulates rate of osteoblasts and bone growth •Calcitonin-promotes calcium deposits in bone and inhibits osteoclast activity •Sex Hormones-stimulate osteoblasts; promote epiphyseal plate growth/close •Parathyroid Hormones-increases blood calcium levels •Calcitriol-stimulates absorption of calcium ions from small intestine to blood INHIBIT BONE GROWTH, INCREASE BONE RESORPTION •Glucocorticoids-increase bone loss, in kids impair bone growth w/ high glu lvl •Serotonin-when levels are high it keeps osteoprogenitors from differentiating into osteoblasts 23. Explain the activation of vitamin D to calcitriol. First understand the

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