Exam 2 Flashcards
How many bones do humans have at birth?
270
List all 6 functions of the skeletal system.
- Support
- Protection
- Movement
- Electrolyte/acid-base balance
- Blood cell production
- Hormone production
What are the 4 different bone shapes?
- Long bones
- Short bones
- Flat bones
- Irregular bones
Define: Trabeculae
Small needle-like pieces in the medullary cavity
Define: Diaphysis
Shaft of the bone
Define: Medullary cavity
Central canal surrounded by a collar of compact bone
Define: Epiphyses
The ends of a bone, are covered with articular cartilage
Define: Epiphyseal plate
The growth plate of hyaline cartilage where bone growth occurs during childhood. Seals and becomes the epiphyseal line in adulthood. (revisit this one for more detail)
Define: Metaphysis
Epiphyseal plate or line
Define: Periosteum
Double-layered membrane around bones
Describe the two layers of the periosteum.
- Fibrous layer: outer layer of dense irregular connective tissue
- Osteogenic layer: inner layer, contains osteoblasts and osteoclasts
The periosteum is richly supplied by nerve fibers, lymphatic vessels, and blood vessels.
Describe the general function of osteoblasts and osteoclasts.
-Osteoblast: secrete osteoid, deposit blood
-Osteoclast: break down blood using HCl
Define: Perforating fibers
Tufts of collagen that extend from the fibrous layer to the bone
Define: Endosteum
Delicate connective tissue membrane; covers trabeculae and canal system in compact bone
Define: Diploe
Endosteum covered trabeculae of spongy bone, only found in the skull
Describe hematopoietic tissue.
AKA red marrow, is found in trabecular cavities of long and short bones. In infants, all bone marrow is red marrow. However in adulthood, blood is only produced in the head of the femur and humerus, flat bones, and some irregular bones.
Osteogenic cells give rise to______.
Osetoblasts
Define: Osteocytes.
Former osteoblasts that have become trapped inside the matrix they produced.
Define: Canalicluli
The structures that connect lacunae (revisit this one)
Osteoclasts have multiple ________.
Nuclei
Describe osteoid.
Osteoblast secretion, makes up 1/3 of the matrix in bone. Made up of collagen fibers and ground substance.
Define: Hydroxyapetite
Calcium phosphates that give bones their exceptional hardness.
Define: Osteon/Haversian System
The structural unit of compact bone, and elongated cylinder that runs parallel to the long axis of the bone. Have growth rings called lamella.
Define: Haversian/Central canal
Runs through the osteon and contains small blood vessels.
Define: Perforating/Volkmann Canals
Run perpendicular to and interconnect with the central canal.
Define: Concentric lamellae
Layers of matrix around the central canal.
Define: Interstital lamellae
Incomplete lamellae that lie in between osteons.
Why is calcium important?
It is required for the proper function of nerve impulses, muscle contraction, blood clotting, and mitosis.
Describe hypocalcemia
Hyperexcitability; muscle spasms
Describe hypercalcemia
Non-responsiveness of the muscles and nerves
Define: Parathyroid hormone
Produced in the parathyroid gland. Responds to low levels of Ca in the bloodstream. This stimulates osteoclasts and inhibits osteoblast activity.
Define: Calcitonin
Produced in the thyroid, responds to high levels of Ca in the bloodstream. Stimulates osteoblasts and inhibits osteoclast activity in response.
Define: Calcitrol
AKA vitamin D, when Ca levels are low it stimulates Ca absorption in the small intestine and increases Ca absorption from bone.
Define: Wolff’s Law
Bone grows in response to mechanical stress placed on it.
Intramembranous ossification forms the _____ and _____.
clavicle; cranial bones
The process of forming bone from fibrous membranes is called ________.
Intramembranous ossification
Before 8 weeks, the skeleton of an embryo is made up entirely of ___________.
fibrous membranes
Precursors to bones are made up of what?
Hyaline cartilage
____________ begins in the 2nd month of embryonic development.
Endochondral ossification
Define: Primary ossification center
The center of the cartilage shaft where ossification begins
Describe: Osteomalacia
A bone disorder in which the bones are poorly mineralized, because of the inadequate distribution of calcium salts. This causes bones to be weak and soft that may bend under weight. Can be caused by lack of dietary Ca or vitamin D.
Describe: Osteoporosis
The process of bone resorption exceeds bone deposition, which leads to a decrease in bone mass. Post-menopausal women are the largest risk for this disease.
Describe: Paget’s Disease
Haphazard and excessive bone deposition and resorption. Lots of spongy bone in relation to compact bone, ratio is off.
Define: Comminuted fracture
The bone is fragmented into three or more pieces.
Define: Compression fracture
Bone is crushed/sandwiched.
Describe: Hematoma formation
(Bone repair)
Bleeding at the sight of a fracture causes swelling at the area.
Describe: Fibrocartilaginous callus formation
(Bone repair)
Capillaries, osteoblasts, and osteoclasts invade the hematoma. Phagocytic cells clear debris; chondrocytes differentiate and form a cartilaginous matrix.
Describe: Bony callus formation
(Bone repair)
In about a week, the fibrocartilaginous callus will begin to be converted into bone.
What is the step-by-step process of intremembranous ossification?
- Mesenchymal cells line up around vessels and become osteoblasts. Osteoblasts secrete osteoid.
- Osteoid tissue hardens and traps osteoblasts in the hardening matrix. Mesenchyme condenses to form periosteum. Matrix begins to take the shape of trabeculae.
- Osteoblasts continue depositing bone and fill in spaces b/t the trabeculae. Compact bone forms at the surface with spongy bone in the middle.
What bones are formed via intramembranous ossification?
Cranial bones and clavicles.
What is the step-by-step process of endochondral ossification?
- Mesenchymal cells form hyaline cartilage covered in perichondrium. Perichondrium produces more chondrocytes and the model grows in size.
- Perichondrium becomes vascularized and becomes the periosteum. Osteoblasts are produced and begin to deposit bone around the diaphysis which forms a bone collar. The bone collar triggers the primary ossification center to form. Chondrocytes hypertrophy, signaling the matrix to calcify.
- Chondrocytes die and leave open cavities that are invaded by periosteal buds (contain arteries, veins, nerves, osteogenic cells, and osteoclasts). Osteogenic cells become osteoblasts and secrete osteoid on calcified cartilage, which makes early spongy bone.
- Osteoclasts break down bone in the center of the diaphysis, creating the medullary cavity. The diaphysis elongates as cartilage at the epiphysis calcifies and is dissolved by osteoclasts. Secondary ossification centers occur at one or both epiphyses. (Bone at birth)
- Periosteal bud enters secondary stage and begins to form spongy bone. (Childhood to adolesence)
The precursors to bones formed via endochondral ossification are made of ________.
Hyaline cartilage
