Chapter 6: Bone and Skeletal Tissues Flashcards
What are the three kinds of cartilage, where are they found, and how do they differ?
Hyaline Cartilage: Found in articular joints, glassy appearance with mostly matrix and dots, most abundant type, collagen fibers only (chondrocytes)
Elastic Cartilage: Found in the ear, epiglottis, and tip of nose. Can be manipulated and will return to original shape, elastic fibers only.
Fibrocartilage: Found in menisci of knee, vertebral disks. Contain thick collagen fibers, has great tensile strength.
What are the four ways that cartilage and bone differ from one another?
- VASCULARITY:
- Cartilage is avascular (slow to repair, receives nutrients via diffusion).
- Bone is vascular (faster to repair, receives nutrients from the nutrient vessels in blood called canaliculi). - COMPOSITION:
- Cartilage is composed mainly of water (allows for resilience).
- Bone is mineralized, composed of collagen, calcium phosphate, and calcium carbonate to make bone rigid. - CELL TYPES:
- Immature cartilage cells are called chondroblasts, mature cartilage cells are called chondrocytes. Chondrocytes are trapped in their own matrix, reside in chambers called lacunae, receive nutrients via diffusion.
- Immature bone cells are called osteoblasts, and mature bone cells are called osteocytes. Osteocytes are trapped in their own matrix, reside in chambers called lacunae, receive nutrients via tiny canals called canaliculi. - INNER/OUTER LAYERS:
- Cartilage seperates itself from other tissue by a 2-layer perichondrium (outer layer dense irregular tissue with a cellular inner layer, the endosteum, than contains stem cells). Delivery center for nutrients and oxygen to then diffuse through the cartiligenous matrix to reach each cell.
- Bone is lined by a 2-layer periosteum (outer layer is fibrous, inner endosteum layer is cellular for bone repair). Tendons attach to the outer periosteum of bone.
What are the functions of bone and the skeletal system?
- SUPPORT: Bone provides structural support and serves as site of attachment for tendons and ligaments.
- PROTECTION: The skeleton protects vital organs.
- ANCHORAGE: Muscles attach to bone by tendons, allowing for movement.
- MINERAL STORAGE: Bone stores several minerals (calcium and phosphorus) for strength, release/absorb this as needed to maintain homeostasis.
- BLOOD CELL FORMATION: Hematopoiesis = the production of new platelets, red, and white blood cells within the RED bone marrow.
- TRIGLYCERIDE (FAT) STORAGE: Lipids are stored in YELLOW bone marrow as an energy reservoir, not present at birth but develops over time.
- HORMONE PRODUCTION: Bone produces osteocalcin that regulates insulin secretion, glucose homeostasis, and energy expenditure.
What is the difference between yellow bone marrow and red bone marrow?
YELLOW: Stores lipids used for energy, not present at birth but develops overtime. Located in the diaphysis.
RED: Where hemotopoiesis occurs to make platelets, red, and white blood cells. Located in trabecular cavities of spongy bone.
What is a sesamoid bone and where do they form?
Sesamoid bones develop beneath tendons (around joints) to shield the tendons from wear and tear. They slightly lift the tendon away from the bone to enhance the muscle’s mechanical leverage during movement at the joint.
Label.
The extracellular matrix of bone consists of what structures?
ground substance, water, collagen fibers secreted by osteoblast cells that build a framework into which crystals of hydroxyapatite (hardening/calcification minerals) are deposited.
What are the four cells types that make up bone, and what are their functions?
Osteogenic cells: Stem cells that develop into osteoblasts. Only bone cells that undergo mitosis.
Osteoblasts: Young bone cells that secrete a soft bony matrix called osteoid (unmineralized bone). Responsible for triggering calcification.
Osteocytes: Primary mature bone cells entrapped in the mineralized bony matrix. Enclosed in a lacuna, they communicate with each other through canaliculi.
Osteoclasts: Destroyer of bone. Derived from monocytes, they are performing bone remodeling by resorbing the bony matrix while the osteoblasts are simultaneously adding bone.
What are the two different kinds of bone? How do they differ in their organization and in their locations in the body?
Spongy Bone: The stringy, spongy interior of bones that lack osteons, has a framework called trabeculae, and is always covered by compact bone.
Compact Bone: The thicker outside of bones with a basic structural unit known as the Osteon/Haversian system.
Label the parts of an osteon:
Nerve, Lacunae, Canaliculi, Artery, Central Canal, Osteocyte in a Lacuna, Vein, Lamellae
What is ossification? What is the difference between endochondral and intramembranous ossification?
The process of turning soft osteoid into hard bone.
Endochondral ossification: The process where bone tissue replaces a cartilage model, primarily seen in the development of long bones. It starts with a hyaline cartilage template that gradually transforms into bone.
Intramembranous ossification: The process by which flat bones like the skull form directly from mesenchymal tissue, without involving cartilage. Mesenchymal cells turn into osteoblasts, which create bone matrix.
What is a primary and secondary ossification center?
A primary ossification center is the first area of bone formation, typically located in the diaphysis (shaft) of a long bone. It begins during fetal development.
A secondary ossification center forms later, usually after birth, in the epiphyses (ends) of the bone, allowing further bone growth.
What are basic steps involved in intramembranous ossification?
- Development of the Ossification Center
- Mesenchymal cells group to form an ossification center to transform from osteogenic cells to osteoblasts that secrete a bone matrix to surround them - Calcification
- Osteoblasts transform into osteocytes when trapped in their matrix. They extend processes into canaliculi to extract calcium and minerals, facilitating calcification of the extracellular matrix. - Formation of Trabeculae
- As the matrix calcifies, trabeculae (spicules) fuse to form spongy bone. Blood vessels grow into the spaces in between. - Periosteum Development
- Mesenchymal cells form the periosteum along the outside of the bone. Within the periosteum, osteoblasts form a
thin layer of compact bone that surrounds the spongy bone.
What are the two primary ways in which bone grows?
- Longer, when bone replaces cartilage on the diaphyseal side of the growth plate or when cartilage grows on the epiphyseal side of the epiphyseal plate (the side of the growth plate closer to the
epiphysis). - Thicker, when osteogenic cells form new osteoblasts along the outside of the bone (appositional growth).
When / how does bone growth stop?
Bone growth stops when cartilage production ceases around the ages of 18 to 21. When all the cartilage (i.e. on the epiphyseal plate) becomes bone, bone growth stops.
