Chapter 7: Bone Tissue Flashcards
What is the study of bone called?
Osteology
What are your most durable remains in bone?
Bones and teeth
What are the functions of the skeleton?
- Skeleton is living (it responds to stress in the body)
- Support
- Protection
- Movement
- Electrolyte balance (calcium and phopshate)
- calcium is usually the concern here
- Acid-base balance
- (buffers blood against pH changes by alternating carbonate and phosphate salt levels)
- Blood formation (hemopoiesis)
- makes RBC, WBC, and platelets
What is the definition of bone?
Bone (osseous tissue): connective tissue with the matrix hardened by calcium phopshate and other minerals
Define mineralization or calcification.
The hardening process of bone.
What do individual bones consist of?
Individual bones are organs and they consist of bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue.
What are the types of bones and some examples?
- Flat bones (sternum, skull bones)
- Long bones: bones that are longer than wide (mostly arms and legs)
- Short bones: length and width are approximately equal (carpals and tarsals)
- Sesamoid bones: bones you develop in a tedon or ligament due to high stress; unnamed (one in carpal, one in foot) (exceptions: patella)
- sutural bones: usually unnamed (e.g. back of head, lamboid formed by small cracks coming together)
- Irregular bones: everything else (e.g. vertebrae)
What is the structure of a bone?
Epiphysis: the end of the bone, has proximal end and distal end
Diaphysis: shaft of bone
Epiphyseal Line (aka metaphysis): separates epiphysis from diaphysis
- this called the “growth plate” until growth is dome
Articular cartilage: white, hyaline cartilage at the ends of moveable joints
Spongy bone on the outer layer, compact bone on the inner layer, marrow cavity
What are the general features of bone?
- articular cartilage (hyaline)
- nutrient foramina (holes where blood vessels come in)
- Periosteum
-
endosteum (thin layer of reticular connective tissue lining marrow cavity)
- contains osteoblasts and osteoclasts
-
epiphyseal plate (enables growth in length of bone)
- made of hyaline cartilage
- when finished, turns into epiphyseal line
What are the general features of flat bones?
- Sandwich-like
- two layers of compact bone with a middle layer of spongy bone
- diploe: spongy middle layer
- absorbs shock
- marrow spaces lined with endosteum
- red, make blood here
What are the two layers of periosteum and their general features?
- Outer fibrous layer made of collagen
- some fibers continuous with tendons
- perforating fibers: penetrate into bone matrix
- Inner osteogenic layer
- important to bone growth and healing of fractures
Describe “trabeculae”
Trabaculae (thin plates) is calcified and hard, but it is named for its spongelike appearance. It is covered with endosteum and permeated by spaces filled with bone marrow (where blood is made).
What are the 4 types of bone cells and their general features?
- Osteogenic cells
- stem cells that perform mitosis and become osteoblasts
- Osteoblasts: bone forming cells
- Osteocytes: mature bone cells
- found in pockets called lacunae
- connected to each other by gap junctions and canaliculi (cracks in bone to connect cells)
- some reabsorb bone matrix and others deposit it (regulates bone modeling)
- Osteoclasts
- the “oddball”; it is not osteogenic
- derived from fusion of WBC
- usually multinucleate
- secretes enzymes and acids for resorption (the break down of bone)
What are the main 2 steps involved in the making of bone? How does resorption work?
- Secrete protein (collagen fibers)
- need lots of ATP and amino acids
- cell needs lots of Rough ER and Golgi
- Deposit calcium salts (from blood)
- process is like making rock candy
- Enzymes dissolve collagen via hydrolysis and acids dissolve salt, which returns to the blood
What are the two portions of bone matrix and their general features?
- Organic portion (1/3 of bone)
- Collagen, carbohydrate-protein complexes
- synthesized by osteoblasts
- responsible for the flexibility of bone
- Inorganic portion (2/3 of bone)
- 85% hydroxyapatite (calcium phosphate)
- 10% calcium carbonate
- 5% other minerals (floride, sodium, etc.)
- Responsible for the hardness of bone
What happens to bone under the following conditions: mineral deficiency and defect in collagen deposition?
Mineral deficiency: soft bones (in adults causes pain, in children causes deformity as seen in Rickets)
Collagen: no flexibility (brittle bone disease), bones snap easily
What are the components of a Haversian System or an Osteon?
- Lamella
- columns of the matrix (mainly collagen) that are weight bearing
- concentric, circumferential, and interstitial lamella
- Central (Haversian) canal)
- contains blood vessels and nerves
- Perforating (Volkmann’s) canals
- channels that connect blood and nerves from periosteum to the central (Haversian) canal
What is the structure of spongy bone?
- Lattice of bone covered with endosteum
- trabeculae (thin plates of bone)–develop along the bone’s line of stress
- spicules (slivers of bone)
- spaces filled with red bone marrow
- few osteons, no central canals
- provides strength with minimal weight
- will crush first if depleted calcium (like in osteoperosis)
Where is red marrow (hematopoietic tissue) located in children and in adults?
Children: medullary cavity and all areas of spongy bone (much will be converted to yellow marrow over time)
Adults: head of the femur and the humerus, diploe (spongy bone) of flat bones, some irregular bones (e.g. hip and vertebrae)
How does intramembranous ossification work and what are soem examples of it?
- mesenchymal cells turn to osteoblasts turn to osteocytes, which form spongy bone
- This forms the flat bones of the skull, clavicles, and ossifies the fontanels
- Most of these bones are remodeled (destroyed and reformed) as we grow to adult size
What are the two types of endochondrial ossification and how do they work?
- Primary ossification: works on the diaphysis (shaft) of bone
- this is the first part to be destroyed and turned into bone
- Secondary ossification: works on epiphysis (ends of bones)
- this turns cartilage into bone from the center outward
- cartilage cells undergo mitosis and push the epiphysis away from the diaphysis
- cartilage cells die and are replaced by bone
- When plate is finished, no more cartilage plate: now epiphyseal line
- bone can no longer grow in length; plate is closed
- articular cartilage should stay for life
What are bone fractures and their classifications?
- Stress fracture: break caused by abnormal trauma to a bone
- Pathological fracture: break in a bone weakened by disease (cancer or osteoperosis)
- Classified by structural characteristics
- displaced v. nondisplaced
- pulled out of normal alignment / not
- open v. closed / simple v. compound
- Open = open to skin, closed = closed to skin
- displaced v. nondisplaced
How do fractures heal?
- The fracture in bone creates a hematoma and the bone bleeds a lot
- The bone deposits collagen and forms both a soft callus and fibrocartilage
- The bone forms a hard callus and spongy bone
- The bone remodels into compact bone and is healed
What is osteoperosis and what problems does it cause?
- Osteoperosis is the most common bone disease
- It affects spongy bone the most
- (spongy bone is most metabolically active)
- Trabiculae get crushed and the bone heals that way
- Inhibits resorption of estrogen by osteoclasts
- estrogen highly important for bone density
- Individuals are subject to fractures of hip, wrist, and vertebral column
- Most affected
- post menopausal women and underweight, young female athletes
- Example:
- Widow’s hump (deformity of spine due to vertebral bone loss)
