Bio 141 - Exam 3 (Chapter 7)

Briefly explain the formation and resorption of bone matrix

Bone formation begins when osteoblasts secrete the initial semisolid osteoid. Calcification occurs to the osteoid when hydroxyapatite crystals deposit in teh bone matrix. Bone resorption is a process where bone matrix is destroyed by substances released from osteoclasts into the extracelluar space. Proteolytic enzymes (released from lysosomes w/in the osteoclasts) digest the organic components of the matrix, while HCl dissolves the mineral parts.

Identify the two most common types and locations of cartilage within the skeletal system

Cartilage is a semi-rigid connective tissue that is more flexible than bone. Two most common subtypes are: - Hyaline cartilage (attaches to the ribs of the sternum, covers the ends of some bones (articular cartilage), and is the cartilage w/in growth plates. Provides a model for the formation of most of the bones in the body. - Fibrocartilage (weight-bearing cartilage with withstands compression; forms invertebral discs, the pubic symphysis, and cartilage pads of the knee joints

Name the basic structural and functional unit of compact bone

Compact bone is composed of small cylindrical structures called osteons, which are the primary functional and structural unit of mature compact bone.

Identify the role of ligaments and tendons associated with the skeletal system

Ligaments are dense regular connective tissue that anchor bone to bone. Tendons are dense regular connective tissue that anchor muscle to bone.

Define intramembranous ossification, and identify the bone produced by it.

Intramembranous ossification is "bone growth within a membrane," named b/c of the mesenchyme in these areas. Intramembranous ossification procuddes flat bones of the skull, some of the facial bones (zygomatic bone, maxilla), the mandible, the central part of the clavicle.

Explain why it is more difficult to heal damaged cartilage than damaged bone tissue

It is more difficult to heal damaged cartilage because mature cartilage is avascular. W/o a regular and steady blood supply, healing takes much longer.

Given a diagram of a longitudinal section of a long bone, identify the following structures: - diaphysis - epiphysis - metaphysis - epithelial line - epiphyseal plate - articular cartilage - compact bone - spongy bone - periosteum - endosteum - medullary cavity

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Given a picture of a bone, identify the type of bone based on its shape

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Name two types of bone connective tissue

- Compact bone (also called dense bone or cortical bone): relatively dense connective bone tissue that appears white, smooth, and solid. It makes up approx 80% of the total bone mass - Spongy bone (also called cancellous or brabecular bone) is located internal to compact bone, appears porous, and makes up approximately 20% of the total bone mass.

List the four categories of bone as determined by shape

- Long Bones: greater in length than in width. They have an elongated, cylindrical shaft (diaphysis) and are found in the upper limbs (arm, forearm, palm, fingers) and lower limbs (thigh, leg, sole of the foot, toes). Vary in size. Are the most common bone shape. - Short bones: length is nearly equal to width. Examples include carpals (wrist bones) and tarsals (foot bones). Sesamoid bones are small, sesame-seed shaped bones along the tendons of some muscles. The patella is the largest sesamoid bone. - Flat bones: flat, thin surfaces that may be slightly curved. Provide extensive surface for muscle attachment and protection of underlying soft tissue. Ex: the roof of the skull, scapulae (shoulder blades), sternum (breast-bone), and ribs. - Irregular bones: have elaborate, sometimes complex shapes and do not fit the preceding categories. Exs: vertebrae, ossa coxae (hip bones), several bones in the skull, such as ethmoid, sphenoid, and sutural bones.

List the four types of bone cells and describe the function of each.

- Osteoprogenitor cells: stem cells derived from mesenchyme. When they divide, another stem cell is produced along with a "committed cell" that matures to become an osteoblast. - Osteoblasts: formed from osteoprogenitor cells; exhibit a cuboidal shape and have abundant rough ER and golgi appartatus. Perform the function of synthesizing and secreting initial semisolid organic form of bone matrix (called Osteoid). Osteoid later califies as a result of salt cyrstal deposition. As a result, osteoblasts become entrapped in their matrix and then differentiate as osteocytes. - Osteocytes: mature bone cells derived from osteoblasts that have lost their bone-forming ability when enveloped in calcified osteoid. Responsible for maintaining bone matrix and detecting mechanical stress on bone. - Osteoclasts: large, multinuclear, phagocytic cells. Derived from fused bone marrow cells; exhibit a rough border where they contact bone (increases their surface area). Often located w/in or adjacent to a depression or pit (called a resorption lacuna). Involved in breaking down bone in bone resporption.

List the four general functions of bone

- Support and protection: provides structural support to the body and protection of many delicate tissues and organs - Movement: Bones serve as attachment sites for skeletal muscles, soft tissue, and some organs. Muscles attached to the bones of the skeleton contract and exert a pull on the skeleton that then functions as a system of levers. - Hemopoiesis: the process of blood cell production; occurs in red bone marrow connective tissue that contains stem cells that form bolood cells and platelets. - Storage of mineral and energy reserves: most of the body's reserves of the minerals calcium and phosphate are stored w/in and released from bone. (Calcium is essential in muscle contraction and the release of neurotransmitter from nerve cells. Phosphate is a structural component of ATP, nucleotides, and phospholipids and plasma membrane.)

List the organic and inorganic components of bone matrix and describe the functions of each.

- The organic component of bone matrix is osteoid. Osteoid is composed of colagen protein plus semisolid ground substance of proteogycans adn glycoproteins that suspend and support the collagen fibers. Thsi gives bone its tensile strength by resisting stretching and twisting, contributing to overall flexibility. - The inorganic component of bone is made up of salt crystals of calcium phosphate (Ca3(PO4)2). Calcium phosphate and calcium hydroxide interact to form cyrstals of hydroxapatite. Crystals deposit aroudn long axis of collagen fibers int he extracellualr matrix, which then harden the matrix and accoutn for the rigidity of bone.

Describe the function of the following components of an osteon: - central canal - perforating canals - canaliculi - lacuna - concentric lamellae - interstitial lamellae

- central canal: cylindrical channel that lies int eh center of the osteon and runs parallel to it. (Blood vessels and nerves that supply the bone are w/in the central canal) - perforating canals: resemble central canals, but run perpendicular to central canalst o help connect multiple central canals within different osteons. - canaliculi: tiny, interconnecting channels w/in the bone connective tissue that extend from each lacuna, travel throught eh lamellae, and connect to other lacunae and central cal. Houses osteocyte projections that pemit contact and communication. Nutrients, minerals, gases, and wastes are transported through. - lacunae: smalls paces that house each osteocyte. - concentric lamellae: rings of bone connective tissue that surround the cnetral canal and form the bulk of the osteon. Fibers are oriented at 90 degree differences from teh fibers around them, which adds to strength and resilience of bone. - interstitial lamellae: components of compact bone that are b/t osteons or the leftover parts that have bene partially resorbed. they are incomplete and typically have no central canal.

Describe the function of the following structures: - epiphyseal plate - epiphyseal line - periosteum - endosteum - medullary cavity

- epiphyseal plate: growth plate - epiphyseal line: a thin, defined area in adults that is the remnant of the epiphyseal plate - periosteum: tough outter sheath that covers the surface of bone. Has 2 layers that protect bone, serve as an attchment site, etc. - endosteum: Incomplete laeyer of cells that covers all internal surfaces of one w/in the medullary cavity. Contains osteoblasts, osteoclasts, and osteoprogenitor cells. - medullary cavity: the hollow, cylindrical space w/in the diaphysis. Contains blood marrow.

Describe appositional growth

Appositional growth is an increase in width along the cartilage's edge or periphery. Occurs in 3 steps: 1. Undifferentiated stem cells at eh internal edge begin to divide. 2. New undifferentiated cells and committed cells that differentitate into chondroblasts are formed. Condroblasts are located at the periphery of the old cartilage where they begin to produce and secrete new cartilage matrix. 3. Chondroblasts, as a result of matrix formation, push apart and become chondrocytes, each occupying its own lacuna. Cartilage continues to grow at the periphery as chondrocytes continue to produce more matrix.

Describe blood supply and innervation (nerve supply) of the bone

Bone is highly vascularized, especially in areas containing spongy bone. Blood vessels enter ones from the periosteum. Typically only 1 nutrient artery enters and 1 nutrient vein exits -- both via a small opening called a nutrient foramen.

Describe how the location of red and yellow bone marrow differs between adults and children

In children, red bone marrow is located in the spongy bone of most of the body, as well as in the Medullary cavity of long bones. Red bone marrow degenerates as children age, and the marrow primarily int eh medullary cavities of long bone turns to a fatty substance of yellow bone marrow. As a result, adults have red bone marrow only in selected portions of the axial skelton, such as the flat bones of the skull, the vertebrae the ribs, sternum, and ossa coxae (hip bone).

Expalin how the red and yellow bone marrow work in severe anemia

In severe anemia (a condition in which erythrocyte numbers are lower than normal), resulting in insufficient oxygen reaching the cells of the body, yellow bone marrow may be triggered to convert back to red bone marrow, a change that facilitates production of additional erythrocytes.

Describe interstitial growth

Interstitial growth is a growth in length. It occurs w/in the internal regions of cartilage in 4 steps: 1. Chondrocytes housed w/in lacunae are stimulated to undergo mitotic cell division. 2. After cell division, 2 cells occupy a single lacuna. they are now called chondroblasts. 3. As chondroblasts begin to synthesize and secrete new cartilage matrix, they are pushed apart. They then reside in their own lacuna and are called chondrocytes. 4. Cartilage continues to grow as chondrocytes continue to produce more matrix.

Describe the characteristics of each type of bone based on its shape

Long bone features an elongated, usually cylindrical shaft called a diaphysis, which provides for the leverage and major weight support of the long bone. Extending inward along the length of the diaphysis are spicules (spike-like structures) of spongy bone. The hollow, cylindrical space w/in the diaphysis is the medullary cavity. @ the end of each long bone is an expanded, knobby region called the epiphysis. A proximal epiphysis is the end of the bone closest to the body trunk; a distal epiphysis is farthest from the trunk. An epiphysis is composed of an outer thin layer of compact bone and an inner layer of spongy bone. The spongy bone w/in the epiphysis resists stress. Covering the joint surface is a thin layer of hyaline cartilage called the articular cartilage, which reduces friction and absorbs shock. The metaphysis is the region in mature bone b/e the diaphysis and epiphysis. It contains the epiphyseal plate (growth plate), which is a thin layer of hyaline cartilage that provides for continued length-wise growth of the bone. The remnant of the epiphyseal plate in adults is a thin defined area called the epiphyseal line. - Short, flat, and irregular bone are composed of compact bone; interior is entirely spongy bone w/ no medullary cavity.

Briefly describe bone marrow transplant in leukemia patients

Once matched closely for bone marrow, donor marrow is harvested from the hip bone and injected into the blood of the recipient, where they wll be transported to the normla locations for red bone marrow.