Chr. 6 - Skeletal System Flashcards
[6.1] What is a bone?
An organ providing structural framework made of several connective tissues: osseous tissue, cartilage, dense connective tissue, adipose; as well as epithelium and nervous tissue.
[6.1] What are the functions of the skeletal system?
Support, protection, assistance in movement, mineral homeostasis, blood cell production, and triglyceride storage.
[6.1] How does the skeletal system provide support?
By providing attachment points for tendons and supporting soft tissue with rigid structure.
[6.1] How does the skeletal system provide protection?
Creating rigid structures covering vital organs and tissues.
[6.1] How does the skeletal system provide assistance in movement?
Provide anchor points for muscles during contractions.
[6.1] How does the skeletal system provide mineral homeostasis?
Extracellular matrix of bone contains minerals that are released from or absorbed into the bone to balance out levels throughout the body.
[6.1] How does the skeletal system provide blood cell production?
Red bone marrow generates RBCs, WBCs, and platelets through hemopoiesis.
[6.1] How does the skeletal system provide triglyceride storage?
Triglycerides are stored in yellow bone marrow, acting as chemical energy reserves.
[6.2] What are the typical sections of a long bone?
Diaphysis, epiphyses, metaphyses, articular cartilage, periosteum, medullary cavity, and endosteum
[6.2] What is a diaphysis?
The main, central body of a bone.
[6.2] What are the metaphyses?
The regions between a bones diaphysis and epiphyses.
[6.2] What are the epiphyses?
The proximal and distal ends of the bone.
[6.2] What is the articular cartilage of a bone?
A thin layer of hyaline cartilage covering the epiphyses of a bone where it articulates with another.
[6.2] What is the periosteum?
Tough connective tissues sheathing the bone where articular cartilage is absent. Consists of an outer fibrous layer and an inner osteogenic layer.
[6.2] What is the medullary cavity?
The hollow space within the diaphysis containing red or yellow bone marrow.
[6.2] What is the endosteum?
A thin membrane lining the medullary cavity.
[6.3] Describe an osteoprogenitor cell.
Unspecialized bone stem cells derived from mesenchyme, develop into osteoblasts.
[6.3] Describe an osteoblast.
Cells synthesizing and secreting extracellular matrix and initiating calcification.
[6.3] Describe an osteocyte.
Mature bone cells, maintain metabolism and functional activities.
[6.3] Describe an osteoclasts.
A large cell composed of many monocytes containing lysosomal enzymes and acids that deconstruct bone matrix to maintain mineral homeostasis.
[6.3] What is compact bone tissue?
Bone tissue composed of tightly packed repeating structural units called osteons
[6.3] What are osteons? List the components.
Structural units shaped like a tube surrounding blood vessels and nerves. Formed of concentric lamellae, lacunae, canaliculi, and central canals.
[6.3] Describe lamellae.
Concentric rings of extracellular matrix formed around central canals.
[6.3] Describe lacunae.
Small spaces between lamellae housing osteocytes.
[6.3] Describe canaliculi.
Networks of tiny channels allowing the processes of osteocytes to reach other cells for nutrient exchange.
[6.3] Define central canals.
Canals located in the center of osteons containing blood vessels and nerves.
[6.3] What are interstitial lamellae?
Lamellae located between osteons, also containing osteocytes.
[6.3] Describe interosteonic canals.
Blood vessel and nerves that run transverse through osteons.
[6.3] What are perforating fibers?
Fibers connecting the periosteum to the osteons of compact bone tissue directly deep to it.
[6.3] What is spongy bone tissue?
Bone tissue containing lamellae in columns without central canals, forming a series of connected branches rather than pillars/tubes.
[6.3] What is the purpose of spongy bone tissue?
To decrease weight of a bone, and to provide support and protection for the bone marrow found inside.
[6.4] What are periosteal arteries?
Small arteries accompanied by nerves entering through interosteonic canals.
[6.4] What are the nutrient artery and the nutrient foramen?
A large artery entering the diaphysis; the hole through which the nutrient artery passes.
[6.4] What are the metaphyseal arteries and the epiphyseal arteries?
Arteries that enter a bone at a location respective of their names.
[6.5] What is ossification?
The process of bone formation.
[6.5] What are the situations where bone formation occurs?
- Initial formation in embryo/fetus.
- Growth during infancy to adolescence.
- Remodeling of bone.
- Repair of bone.
[6.5] What are the types of bone formation in embryonic/fetal development?
Intramembranous ossification and endochondral ossification.
[6.5] Describe the process of intramembranous ossifcation.
- Cells of mesenchyme cluster and differentiate into osteoblasts, forming the ossification center.
- Osteoblasts secrete extracellular matrix until enveloped, at which point they mature into osteocytes.
- Extracellular matrix forms trabeculae and red bone marrow forms from red bone marrow.
- Mesenchyme concurrently condenses at the periphery of the bone, developing the periosteum and developing a layer of compact bone overlaying the spongy bone tissue.
[6.5] Describe steps 1, 2, and 3 of the process of endochondral ossification.
- Mesenchyme clusters in the shape of the bone and differentiates into chondroblasts, developing a cartilage model of the bone covered in a perichondrium.
- Chondroblasts deep in extracellular matrix mature into chondrocytes and divide, growing the cartilage model through interstitial growth. The periosteum carries out appositional growth.
- A nutrient artery penetrates the periosteum and calcifies the cartilage model while stimulating osteoprogenitor cells. The primary ossification center forms, a region where bone first forms and extending its development inward
[6.5] Describe steps 4, 5, and 6 of the process endochondral ossification.
- Osteoclasts break down bone within the center of the spongy bone tissue forming, creating the medullary cavity.
- Branches of epiphyseal arteries penetrate the epiphyses and calcify the cartilage around them. This forms the secondary ossification center. where spongy bone tissue develops without a medullary cavity. Bone formation proceeds outwards.
- Cartilage covering the epiphyses develops into articular cartilage.
[6.5] What is interstitial growth of a bone during endochondral ossification?
Lengthwise cartilage growth by secretion of extracellular matrix and cell division of chondrocytes.
[6.5] What is appositional growth of a bone during endochondral ossification?
Widthwise growth of a bone by secretion of extracellular matrix from chondroblasts in the perichondrium.
[6.5] How does bone grow in length during infancy to adolesence?
- Interstitial growth of cartilage on the epiphyseal side of the epiphyseal plate.
- Replacement of cartilage on the diaphyseal side of the epiphyseal plate.
[6.5] Describe each of the zones of the epiphyseal plate.
- Zone of resting cartilage - Layer nearest epiphysis consisting of sparse chondrocytes.
- Zone of proliferating cartilage - Layer above resting cartilage, involves chondrocytes undergoing interstitial growth.
- Zone of hypertrophic cartilage - Layer above proliferating cartilage, consists of large, matured chondrocytes in columns.
- Zone of calcified cartilage - Layer above hypertrophic cartilage, consists of dead chondrocytes in calcified extracellular matrix. Osteoclasts clear away calcified cartilage, and osteoblasts replace it during endochondral ossification.
[6.5] What is the epiphyseal line?
A bony structure formed when all cartilage has been replaced by bone at the end of adolescent growth.
[6.5] How does bone grow in width during infancy to adolesence?
- Periosteal cells differentiate into osteoblasts, secreting extracellular matrix and maturing into osteocytes.
- Bone ridges form around blood vessels, eventually enclosing them in the central canal.
- This process continues as the periosteum is pushed further away from the medullary cavity.
[6.5] What is the process of bone remodelling?
Ongoing replacement of old bone tissue by new bone tissue.
[6.5] What is bone resorption?
The removal of minerals and collagen fibers from bone by osteoclasts.
[6.5] What is bone deposition?
Addition of minerals and collagen fibers to bone by osteoblasts.
[6.5] Which factors affect bone growth/remodeling?
- Mineral availability.
- Vitamin availability.
- Hormones.
[6.7] What is parathyroid hormone?
A hormone produced by the parathyroid, functions to increase blood calcium.
[6.7] What is calcitriol?
The active form of vitamin D that promotes absorption of calcium from ingested substances.
[6.7] What is calcitonin?
A hormone promoting bone deposition by inhibiting osteoclasts.
