Exam 3: Bone Tissue Flashcards
What are the most abundant mineral salts?
Calcium phosphate and calcium hydroxide
The mineral salts combine to form what?
Crystals of hydroxyapatite
What are the four cell types of bone tissue?
Osteogenic cells
Osteoblasts
Osteocytes
Osteoclasts
Stem cells that divide to give rise to osteoblasts
Osteogenic cells
Type of bone cell that mainly secretes collagen fiber and also initiate calcification
Osteoblasts
Process by which mineral salts are deposited, crystallize, and harden
Calcification
Mature osteoblasts that have become surrounded by the extracellular matrix that secrete as they continue the process of calcification
Osteocytes
Type of large bone cell produced by fusion of many monocytes (a type of WBC) whose ruffled border secretes digestive enzymes (degrades collagen fibers) and acids (degrades mineral salts)
Osteoclasts
Process that degrades and removes mineral salts and collagen fibers by osteoclasts; and where old bone tissue is being broken down.
Bone resorption
Two types of bone tissue
Compact bone
Spongy bone
(Both can be found within a single bone)
Type of bone tissue that have few open spaces w/in the extracellular matrix and organized units called OSTEONS
Compact bone
Type of bone tissue that have many open spaces w/in the extracellular matrix and organized units called TRABECULAE
Spongy bone
Remember:
Compact bone ->
Spongy bone ->
Compact bone -> osteons
Spongy bone -> trabeculae
Parts of the osteon
- central (haversian) canal
- concentric lamellae
- lacuna/e
- canaliculus/canaliculi
Part of the osteon that is the opening for blood vessels
Central (haversian) canal
rings of calcified extracellular matrix in bone tissue
Lamellae
Small spaces between lamellae in which osteocytes occur
Lacuna/lacunae
Small opening radiating from lacunae in which processes of the osteocytes lie
Canaliculus/canaliculi
Difference between osteons and trabeculae
Trabeculae have all parts like the compact bone (osteons) but it doesn’t have central canals
Process where new bone tissue is being formed; process of addition of minerals and collagen fibers by osteoblasts
Bone deposition
Types of bones
Sutural (ex: frontal) Flat (ex: sternum) Irregular (ex: vertebra) Sesamoid (ex: patella) Short Long
What type of bone tissue is in a long bone?
Both compact and spongy tissue
Seven major features of long bone
Diaphysis Epiphysis Metaphysis Medullary cavity Endosteum Articulatar cartilage Periosteum
Cylindrical shaft of the bone
Diaphysis
Distal and proximal ends of the bone
Epiphysis
Regions where diaphysis joins epiphyses &
Includes an epiphyseal growth plate in children which is hyaline cartilage that allows bone to grow in length
Metaphysis
Space within diaphysis that contains yellow bone marrow
Medullary cavity
Epithelial membrane that lines the medullary cavity
Endosteum
Thin layer of hyaline cartilage covering epiphysis where it articulates with another bone
Articular cartilage
Lines the outside of the bone and has an outer fibrous layer and inner cellular (osteogenic) layer
Periosteum
How is blood supplied in long bones?
- Periosteal arteries enter diaphysis through perforating canals
- Supply blood to periosteum and outer compact bone of diaphysis
- Nutrient artery (or arteries) enter medullary cavity (marrow) of diaphysis through nutrient foramen
- Supply blood to inner compact bone and spongy bone of diaphysis
- Metaphyseal arteries supply blood to epiphyseal cartilage
Process of bone formation
Ossification or osteogenesis
When does ossification occur?
During bone development in embryo/fetus
During bone growth in childhood
During remodeling in adult
During bone repair after fracture
How does bone development occurs in embryo/fetus?
Ossification via replacement of preexisting connective tissue with bone
Two mechanisms of ossification
Intramembranous ossification
Endochondral ossification
Mechanisms of ossification where bone forms directly from membranous sheets of embryonic cells
Intramembranous ossification
3 steps of intramembranous ossification
- Development of an ossification center with osteoblasts
- Calcification by osteocytes; Blood vessels become surrounded by bone tissue
- Formation of trabeculae (spongy bone) and red bone marrow; Bone remodeling may later replace some spongy bone with compact bone
Mechanism of ossification where bone forms within hyaline cartilage that develops from embryonic cells
Endochondral ossification
7 steps of endochondral ossification
- Development of cartilage model surrounded by a perichondrium
- Cells of perichondrium convert into osteoblasts and produce sheath of bone tissue
- Fibroblasts in blood vessels differentiate into osteoblasts and produce primary ossification center
- Ossification proceed towards two ends of bone; Spongy bone in center of diaphysis breaks down to form medullary cavity
- Osteoblasts migrate in epiphyses and produce secondary ossification centers
- Articular cartilage and epiphyseal cartilage (plate) develop; Both are composed of hyaline cartilage
- Bone grows in length until puberty, as new cartilage is added to epiphyseal plate and old cartilage is replaced by bone; Interstitial growth
Growth where cell of inner layer of periosteum differentiate into osteoblasts and deposit superficial layers of bone matrix in circumferential lamellae
Appositional growth
Process of fracture and repair of bone
- Formation of fracture. Blood clot formed by severed blood vessels. Death of local osteocytes due to disruption of blood supply
- Fibrocartilaginous callus formation. Cells of periosteum secrete collagen fibers and cartilage to bridge broken edges
- Bony callus formation. Osteoblasts produce spongy bone, which replaces cartilage callus
- Bone remodeling. Osteoclasts remove fragments of broken bone. Compact bone replaces spongy one
Five major functions of bone and skeletal muscle
Support Storage of minerals and lipids Blood cell production Protection Leverage
What is the yellow marrow mainly consists of?
Adipose tissue
What does the red marrow produces via hemopoiesis?
Red blood cells (RBCs)
White blood cells (WBCs)
Platelets
How is the constant level of calcium in blood maintained?
By regulating resorption and deposition of bone
Two hormones that regulate calcium in blood
Parathyroid hormone (PTH) Calcitonin (CT)
Negative feedback involving PTH
Ca2+ in blood decreases
Parathyroid gland cells sense change
Parathyroid gland secretes more PTH
PTH simulate osteoclasts activity
More Ca2+ is released into blood
Negative feedback involving calcitonin (CT)
Ca2+ in blood increases
Thyroid gland cells sense change
Thyroid gland secretes more CT
CT inhibits osteoclasts activity
Less Ca2+ is released into blood
