Bones and skeletal tissues Flashcards
What is perichondrium
Dense connective tissue girdle that contains blood vessels for nutrient delivery to cartilage
What is hyaline cartilage
Provide support, flexibility, and resilience
What is elastic cartilage
similar to hyaline, but contain elastic fibers
what is fibrocartilage
collagen fibers with great tensile strength and it absorbs compressive shock
What is appositional growth of cartilage
Cells secrete matrix against the external face of existing cartilage, increase of diameter
What is interstitial growth of cartilage
Chondrocytes divide and secrete new matrix, expanding cartilage from within, increase of length
What are the 7 functions of bones
Support, protection, storage, blood cell formation, triglyceride storage, and hormone production
What is compact bone
Dense outer layer
What is spongy bone
Also known as trabecular bone, it is a honeycomb for trabeculae and has open spaces filled with bone marrow
What is a diaphysis (shaft)
Compact bone collar surrounding medullary (marrow) cavity, which in adults contains fat (yellow marrow)
What is epiphyses
Expanded ends, spongy bone interior, epiphyseal line, and articular (hyaline) cartilage on joint surfaces
What is periosteum membrane
- the outer fibrous layer (mostly osteogenic cells that give rise to all bone cells except bone destroying cells)
- Nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via nutrient foramina
- Secured to underlying bone by perforating fibers
What is endosteum
- Delicate membrane on internal surfaces of bone
- Contains osteogenic cells
What is the structure of short, irregular, and flat bones
- Periosteum covered compact bone on the outside
- Endosteum covered spongy bone within
- Spongy bone called diploë in flat bones
- bone marrow between the trabeculae
What is hematopoietic tissue
red bone marrow
Describe bone cavities in adults vs infants
In adults trabecular cavities are in the heads of the femur and humerus as well as the diploë in flat bones. In infants medullary cavities and all spaces in spongy bone
What are the cells of the bone
Osteogenic cells, osteoblasts, osteocytes, osteoclasts, and bone-lining cells
What are osteogenic cells
Stem cells in periosteum and endosteum that give rise to osteoblasts and bone lining cells. Develops into an osteoblast basically
What are osteoblasts
Bone forming cells that secrete bone matrix and are responsible for bone growth
What are osteocytes
Mature bones cells, maintain matrix
What are osteoclasts
Cells that break down (resorb) bone matrix
What are bone-lining cells
They’re found on bone surfaces not being remodeled. They look like stem cells, act like osteocytes
What is an osteon of compact bone
A structural unit, it’s the cylinder vascular tunnel that contains the lamella, central canal, perforating canal, lacunae, and canaliculi
What is the lamellae
Weight bearing column like matrix tubes
What is the central canal
Contains the blood vessels and nerves in the osteon
What are the perforating canals
They are at right angles to the central canal, and connects blood vessels and nerves of the periosteum and the central canal
What is the lacunae
Small cavities that contain osteocytes
What is a canaliculi
A hairlike canal that connect lacunae to each other and the central canal. They’re the little things coming off of the lacunae
What is the organic chemical composition of the bone
Osteogenic cells, osteoblasts, osteocytes, osteoids, and osteoclasts
What is the osteoid
- An organic bone matrix secreted by osteoblasts (1/3 of matrix)
- Ground substance (proteoglycans and glycoproteins)
- Collagen fibers that provide tensile strength and flexibility and sacrificial bonds (break easily on impact to dissipate energy which prevents force rising to fracture level)
What is the inorganic chemical composition of the bone
- Hydroxyapatites (mineral salts)
- 65% of bone by mass
- Mainly calcium phosphate crystals
- Responsible for hardness and resistance to compression
What is osteogenesis
Ossification, bone tissue formation
What are the stages of bone development
- Bone formation- Begins in 2nd month of development
- Postnatal bone growth- Until early adulthood
- Bone remodeling and repair- Lifelong
What are the two types of ossification
Intramembranous ossification and endochonral ossification
What does intramembranous ossification do
Membrane bone develops from fibrous membrane, forms most flat bones
What does endochondral ossification do
Cartilage (endochondral) bone forms by replacing hyaline cartilage, forms most of the rest of the skeleton
What is postnatal bone growth
Interstitial bone growth and appositional bone growth
Describe growth in length long bones
Epiphyseal plate cartilage organizes into four important functional zones:
- Proliferation (growth)
- Hypertrophic
- Calcification
- Ossification (osteogenic)
Describe hormonal regulation of bone growth
- Growth hormone stimulates epiphyseal plate activity
- Thyroid hormone modulates activity of growth hormone
- Testosterone and estrogens (at puberty) promote adolescent growth spurts and end growth by inducing epiphyseal plate closure
Describe bone deposit
- Occurs where a bone is injured or added strength is needed
- Requires a diet rich in: Protein, vitamins c d a, calcium, phosphorus, magnesium, and manganese
- Sites of new matrix deposit are revealed by the osteoid seam (unmineralized band of matrix) and calcification front (abrupt transition zone between the osteoid seam and the older mineralized bone)
Describe bone resorption
Osteoclasts in resorption bays. They seal off the area with border against bone, and then secrete lysosomal enzymes and acids.
Describe control of remodeling
- Hormonal mechanisms that maintain calcium homeostasis in the blood
- Mechanical and gravitational forces
What is calcium necessary for in hormonal control of blood
- Transmission of nerve impulses
- Muscle contraction
- Blood coagulation
- Secretion by glands and nerve cells
- Cell division
What is Wolff’s Law
A bone grows or remodels in response to forces or demands placed up it
What are some observations supporting Wolff’s law
- Handedness results in bone of one upper limb being thicker and stronger
- Curved bones are thickest where they are most likely to buckle
- Trabeculae form among lines of stress
- Large, bony projections occur where heavy, active muscles attach
What are the classifications of bone fractures
- Position of ends after fracture
- Completeness of the break
- Whether or not the bone ends penetrate the skin
What are the two types of fractures under position of bone ends after fracture
Nondisplaced and displaced
What are the two types of completeness of break fractures?
Complete and incomplete
What are the two types of bone penetration fractures
- Compound (bone penetrates skin also known as open)
- Simple (bone ends don’t penetrate, aka closed)
What are the 4 stages of healing in a bone fracture
- Hematoma forms
- Fibrocartilaginous callus forms
- Bony callus formation
- Bone remodeling
Describe the hematoma forming stage of healing
-Torn blood vessels hemorrhage
- Clot (hematoma) forms
- Site becomes swollen, painful, and inflamed
Describe the fibrocartilaginous callus forming stage of healing
- Phagocytic cells clear debris
- Osteoblasts begin forming spongy bone within 1 week
- Fibroblasts secrete collagen fivers to connect bone ends
- Mass of repair tissue now called fibrocartilaginous callus
Describe the bony callus formation stage of healing
- New trabeculae form a bony (hard) callus
- Bony callus formation continues until firm union is formed in about 2 months
Describe bone remodeling in healing
- In response to mechanical stressors over several months
- Final structure resembles original
What is osteomalacia and rickets
- Rickets (childhood disease) causes bowed leg and other bone deformities
- Calcium salts not deposited
- Cause: vitamin D deficiency or insufficient dietary calcium
What is osteoporosis
- Loss of bone mass: bone resorption outpaces deposit
- Spongy bone of spine and neck of femur become most susceptible to fracture
What are the risk factors of osteoporosis
- Risk factors are lack of estrogen, calcium or vitamin D; petite body form; immobility; low levels of TSH; diabetes mellitus
What is the treatment and prevention of osteoporosis
- Calcium, vitamin D, and fluoride supplements
- Weight-Bearing exercises throughout life
- Hormone (estrogen) replacement therapy slows bone loss (but increases cancer risk)
- Some drugs increase bone mineral density
What is Paget’s Disease
- Excessive and haphazard bone growth formation and breakdown, usually in spine, pelvis, femur, or skull
- High ratio of spongy bone to compact bone with reduced mineralization
- Unknown cause
- Treatment includes calcitonin and biphosphonates
At birth, most long bones are well _____
ossified
Nearly all bones completely ossified by age ____
25
Bone mass decreases with age beginning in ____
4th decade
Rate of loss in bone determined by _________
Genetics and environmental factors
In old age, bone resorption predominates because of
Homeostatic imbalance
What are the four important functional zones of epiphyseal plate cartilage
Proliferation (growth), Hypertrophic, calcification, and ossification (osteogenic)
Describe hormonal regulation of bone growth
- Growth hormone stimulates epiphyseal plate activity
- Thyroid hormone modulates activity of growth hormone
- Testosterone and estrogens (at puberty) promote adolescent growth spurts and end growth by inducing epiphyseal plate closure
What is bone deposit
Where bone is injured or added strength is needed
Site of new matrix deposit are revealed by the
Osteoid seam and calcification front
What is the osteoid seam
Unmineralized band of matrix for site of new matrix deposit
What is the calcification front
Abrupt transition zone between the osteoid seam and the older mineralized bone in site of new matrix deposit
