BIO 163 Ch. 7 Learning Outline: Bone Structure - PDF

**BIO 163 Ch. 7 Learning Outline** You can also use this outline to take notes in class. You can refer to your textbook for more detailed information on these topics. **[Bone Structure]** 1. **Explain the functions of bone.** Muscle attachment, protection and support of soft tissues. Blood cell...

**BIO 163 Ch. 7 Learning Outline** You can also use this outline to take notes in class. You can refer to your textbook for more detailed information on these topics. **[Bone Structure]** 1. **Explain the functions of bone.** Muscle attachment, protection and support of soft tissues. Blood cell production, and storage of inorganic salts, bear weight and allow movements 2. **[List the categories for classification of bones based on shape and give examples:]** **Long bones**: long with expanded ends; examples: arm and leg bones **Short bones:** almost equal in length and width; examples: bones of the wrist and ankles **Sesamoid (round) bones**: small, nodular bones that develop within a tendon; special type of short bone; example: patella **Flat bones:** plate-like shape with broad surface; examples: ribs, scapula, flattened skull bones Irregular bones: varied shape; examples: vertebrae, some facial bones 3. **[Describe the structure and function for each of the following parts of a long bone:]** a. **Epiphysis:** Expanded ends of bones that form joints with adjacent bones b. **Diaphysis:** The shaft of the bone c. **Articular cartilage:** covers the epiphyses d. **Periosteum:** A tough layer of dense connective tissue, covers the bone, and is continuous with ligaments and tendons e. **Medullary cavity:** The diaphysis contains a hollow chamber **[Microscopic Bone Structure]** 1. **Name the structural unit of compact bone and describe the structure, function and location of compact bone.** **Compact bone:** is a very tightly packed tissue, which makes up the wall of the diaphysis In **compact bone**, **osteocytes** and **extracellular matrix layers** are organized into osteons **(Haversian systems**) that are cemented together **Central canals** contain blood vessels and nerve fibers, and extend longitudinally through the bone tissue **Central canals** of adjacent osteons are interconnected by **transverse perforating (Volkmann's**) canals; these help osteons share blood supply and nerves Compact bone consists of osteons (Haversian systems) with little space between them. Compact bone lies over spongy bone and makes up most of the diaphysis. It functions to protect, support, and resist stress. 2. **Name the structural unit of spongy bone and describe the structure, function and location of spongy bone.** Spongy bone consists of [trabeculae] with numerous red marrow-filled spaces. Spongy bone makes up most of the structure of short, flat, and irregular bones and is also found at the epiphyses of long bones. **Spongy bone** is made of osteocytes and extracellular matrix that lie within **[trabeculae]** (structural unit) 3. **Explain the function of each type of bone cell:** a. **Osteoblast:** Bone-building cells , Osteoblasts deposit a bony matrix around themselves in all directions, forming spongy bone, deposit bone in place of calcified cartilage b. **Osteocyte:** Once the osteoblasts have encased themselves with matrix, they are called osteocytes, are located within chambers called lacunae: pass nutrients and gases through the matrix via tiny canals called canaliculi c. **Osteoclast:** Bone-resorbing cells, break down the calcified matrix **[Bone Functions]** 1. **List the functions of bone.** muscle attachment, protection and support of soft tissues, blood cell production, and storage of inorganic salts, bear weight and allow movement **[Bone Development and Homeostasis]** 1. **Explain the process of intramembranous ossification and list bones in the body which form this way.** 1\) [Development of ossification center] - Mesenchymal cells differentiate into osteogenic cells, which then differentiates into osteoblasts, which secrete organic ECM (collagen fibers). This occurs under the release of specific chemical messengers in certain concentrations.\ 2) [Calcification] - mineral salts such as calcium are deposited by osteoblasts among newly formed network of collagen fibers - ECM calcifies. Osteoblasts then differentiate into osteocytes; calcification continues until osseous tissue becomes too thick, inhibiting osteocytes access to blood vessels to receive nutrients and oxygen.\ 3) [Formation of trabeculae] - death of osteocytes in previous step initiates the reorganization of newly formed osseous tissue into trabeculae to ensure all newly formed osteocytes have access to blood vessels. Trabeculae form around a network of blood vessels to accomplish this.\ 4) [Development of periosteum] - mesenchyme remaining around the surface of the newly formed bone develops into the periosteum; involves remodeling of spongy bone to compact bone. Intramembranous ossification occurs \"within a membrane,\" specifically within mesenchyme, which are connective tissue stem cells; mesenchyme is directly replaced with bone tissue. 1\) Flat bones of the skull (frontal, parietal, occipital, temporal)\ 2) most facial bones (the mandible, for example)\ 3) The sternum\ 4) Medial parts of clavicles. 2. **Explain the process of endochondral ossification and list bones in the body which form this way**. 1.)Formation of cartilage model - occurs early in fetal development, cartilage model is all composed of hyaline cartilage. 2.) Growth of cartilage model - cartilage model grows in length and width, and assumes an appropriate shape for the bone it will eventually become. Osteochondroprogenitor cells, stem cells in the perichondrium, differentiate into osteogenic cells, which then differentiate into osteoblasts, which then begins to calcify the outer surface of the diaphysis of a long bone. This creates a bone collar around the model which restricts chondrocytes access to nutrients and oxygen from surrounding blood vessels. 3.) Development of primary ossification center - primary ossification center develops as a result of the creation of the bone collar, which causes cell death, triggering angiogenesis (formation of blood vessels in tissue). Blood vessels penetrate the model (such as in the diaphyses of long bone), and stimulate differentiation of osteochondroprogenitor cells into osteoblasts which secretes collagen fibers and deposits calcium salts to create the ECM. As a result, bone forms in the center of the diaphysis - the formation of bone in this region eventually merges with the bone collar. 4.) Development of the medullary cavity - Osteoclasts invade newly formed bone and carve out a marrow cavity (these osteoclasts are delivered via the blood supply, has no lineage to osteogenic cells). Spongy bone is then remodeled into compact bone toward the outer surface of the diaphysis - epiphyses of long bone are still cartilage! Track progress 5.) Development of secondary ossification center (occurs at the time of birth) - blood vessels penetrate epiphyses of long bone in response to cell death in this area, which was caused by high metabolic activity in the diaphyses, starving cells in the epiphyses of nutrients and oxygen. Angiogenesis occurs into the proximal epiphyses of the humerus and femur at the time of birth - after birth, the remainder of the epiphyses of long bones will undergo secondary ossification. 6.) Formation of articular cartilage - spongy bone in epiphyses replaces most of cartilage, except for the epiphyseal plate and articular cartilage Endochondral ossification occurs inside cartilage; mesenchyme differentiates into cartilage, which is then replaced with bone tissue. **Bones formed by endochondral ossification** femur, humerus, vertebrae, pelvis, ribs and the medial part of the clavicle 3. **Explain the actions of parathyroid hormone and calcitonin and they relate to the skeletal system.** When blood levels of calcium are low, osteoclasts release calcium from bone When blood calcium is too high, osteoclasts are inhibited, and osteoblasts are stimulated to deposit bone matrix by the hormone calcitonin 4. **Explain bone deposition and bone resorption. These two processes are responsible for the homeostasis of bone tissue.** ***[Deposition:]*** Rebuilding of bone by depositing minerals obtained from bloodstream ***[Bone Resorption:]*** osteoclasts break down the tissue in bones and release the minerals, resulting in a transfer of calcium from bone tissue to the blood 5. **Name the factors that influence bone development.** **Nutrition:** vitamin D is needed for calcium absorption **Hormonal secretions:** Growth hormone: stimulates division of cartilage cells of the epiphyseal plate **Sex hormones:** stimulate ossification of the epiphyseal plates to end growth in height **Physical exercise:** when muscles pull on bones at their attachment sites, it stresses the bone, which will cause it to increase in thickness and strength **[Skeletal Organization]** 1. **Name the groups of bones included in the axial skeleton.** consists of the bony and cartilaginous parts that support the and protect the head, neck and trunk: **Skull:** cranium and facial bones **Hyoid bone:** supports the tongue and aids in swallowing **Vertebral column** **Thoracic cage:** ribs and sternum 2. **Name the groups of bones included in the appendicular skeleton.** Consists of the bones of the upper and lower limbs and the bones that anchor the limbs to the axial skeleton: **Pectoral girdle:** clavicle and scapula **Upper limbs:** humerus, ulna, radius, carpals, metacarpals, and phalanges **Pelvic girdle**: 2 hip bones **Lower limbs:** femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges 3. [ **Know and be able to identify all of the bones and their associated structures which are listed in the "Information to know for Skeletal System Lab Quiz" document on Moodle.**] **[Joints]** 1. Explain the three categories of joint classification based on degree of movement. a. **synarthrotic**: Immovable b. **Amphiarthrotic:** Slightly movable c. **Diarthrotic:** Freely movable 2. Explain the three categories of joint classification based on tissues in joint. a. **Fibrous:** composed of dense connective tissue( synarthrotic) b. **Cartilaginous:** composed of cartilage (Amphiarthrotic) c. **Synovial:** having a complex structure (Diarthrotic) 3. **Explain the structure of a synovial joint.** - Are diarthrotic (allow free movement) - Have a more complex structure than fibrous or cartilaginous joints - Most joints of the skeleton are synovial joints - Articular ends of bones in a synovial joint are covered with hyaline (articular) cartilage - Joint capsule consists of an outer layer of dense connective tissue, and an inner layer, called the synovial membrane - Synovial membrane secretes synovial fluid, which lubricates the joints 4. For the following types of synovial joints, describe their structure, type of movement and give examples: a. **Ball and socket (spheroidal)** - Consists of a bone with a globular or egg-shaped head articulating with the cup-shaped cavity of another bone - Allows widest range of motion, including movement in all planes (multiaxial) - Examples: the shoulder and hip joints b. **Hinge** - A convex surface of a bone fits into a concave surface of another - Allows movement in 1 plane (uniaxial), like hinge of a door - Examples: the elbow and joints between phalanges c. **Pivot (trochoid)** - A cylindrical surface rotates within a ring of bone and ligament - Allows only rotation around central axis (uniaxial) - Examples: joint between the dens of the axis and the atlas 5. Be able to explain all of the movements at joints which are listed in the "Information to know for Skeletal System Lab Quiz" document on Moodle.