Chapter 7 Flashcards
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More info on functions of skeleton
Electrolyte balance
Acid-base balance
Blood formation
1) . The skeleton stores calcium and phosphate ions and releases them into the tissue fluid and blood as needed.
2) . Bone tissue buffers the blood against excessive PH changes by absorbing or releasing alkaline phosphate and carbonate salts.
3) . Red bone marrow is the major producer of blood vessels.
Functions of the skeleton
Support Protection Movement Electrolyte balance Acid-base balance Blood formation
Bones and osseous tissue
Connective tissue in which the matrix is hardened by the deposition of calcium phosphate
Contains blood, bone marrow, cartilage, adipose, neurons and fibrous CT
Four categories of bones
Flat- thin, curved plates
Long- serve as rigid levers that r acted upon by skeletal muscles to produce movement.
Short- bones equal in length and width that produce limited gliding movements.
Irregular bones- bones that don’t fit in any other category.
General anatomy of long bones
- Compact bone
- Marrow cavity
- Spongy bone
- Outer shell of dense white bone tissue.
- Space enclosed by compact bone which contains bone and marrow.
- Loosely organized bone tissue filling the central space of the ends of the bone and the middle of the non-long bones.
Features of long bones
- Diaphysis
- Epiphysis
- Articular cartilage
- The shaft that provides leverage.
- The head at each end of the bone that strengthens the joint and provides added surface area for attachment.
- A layer of hyaline cartilage that covers the joint surface where one bone meet another.
Linings of the bone
- Periosteum
- Some collagen fibers
- Endosteum
- And outer layer of collagen and inner layer of bone forming cells.
- Some of the collagen fibers are continuous with tendons binding muscle to bone.
- Layer of connective tissue that lines the Marrow cavity, covers the surfaces of spongy bone and lines the canal system.
Ephiphyseal plate
Hyaline cartilage in children separating the marrow spaces of the epiphysis and diaphysis, a zone where bones grow in length.
Anatomy of a flat bone
- Two layers of compact bone enclosing a middle of spongy bone.
- The spongy bone may absorb impact of a blow to the cranium even if the outer compact bone is fractured.
Histology of osseous tissue
Four principal types of bone cells
- Osteogenic cells
- Osteoblasts
- Osteocytes
- Osteoclasts
Osteogenic cells
Stem cells in the endosteum and periosteum that multiply continually and give rise to osteoblasts.
Osteoblasts
Bone forming cells that synthesize the organic matter of the bone matrix which is hardened by mineral deposition.
Osteocytes
Former osteoblasts that have become trapped in Lacunae in the matrix they deposited.
Lacunae are interconnected by canaliculi which allows cells to pass nutrients, chemical signals and wastes to one another.
Osteoclasts
Bone dissolving cells found on the bone surface.
They develop from bone Marrow stem cells.
They reside in pits that they have etched into the bone surface.
The matrix dry weight
One third organic and two thirds inorganic matter
The matrix organic matter includes
Collagen and other molecules
The matrix inorganic matter includes
85% hydroxyapatite, a calcium phosphate salt and 10% calcium carbonate with lesser amounts of other matter
What two things is bone a composite of and what does it do?
Collagen which gives it flexibility with tensile strength and
hydroxyapatite giving the strength to support the weight of the body.
Compact bone histology
What is an osteon?
It is a cylinder of tissue surrounding a central canal.
VAN
Van stands for veins, arteries and nerves. (red, blue, yellow)
They always travel together in a van
What are osteons made of?
- Concentric lamellae- which is rings of matrix.
- Central canal- which is passageway containing the nerve, artery and vein.
- Perforating canals- which are passageways that join central canals.
- Where do blood vessels enter the bone tissue?
2. Where do the inner most osteocytes receive nutrients from?
- Through nutrient foramina on the surface which opens into the perforating canals.
- The blood vessels and they pass them along through gap junctions and canaliculi, which are little canals.
What are some facts about spongy bone?
- The bone consists of a lattice of bone called spicules and trabeculae.
- Lamellae but no central canals because no Osteocyte is far from Marrow.
- Spongy bone imparts strength to a bone while adding minimum weight.
- The trabeculae are arranged along the bones lines of stress.
What is bone marrow?
It is the soft tissue that occupies the marrow cavity and the spaces in the spongy bone.
What is red marrow?
It is tissue that produces blood cells in the marrow cavities of children and the spongy bones of the skulll, vertebrae, sternum, hips, etc.
What is yellow marrow?
It is fatty tissue in marrow cavities of most adult bones.
Bone development
Intramembraneous ossification
It produces the flat bones of the skull and most of the clavicle.
What are the 4 stages of intramembraneous ossification?
- Mesenchyme condenses into a layer of soft tissue permeated by blood capillaries and becomes trabeculae.
- Osteoblasts deposit a matrix of collagen, minerals deposit on the matrix, and the cells r trapped becoming a osteocytes.
- Osteoblasts continue to deposit collagen and the bony trabeculae creates spongy bone.
- Trabeculae at the surface continue to calcify until the spaces are filled, converting the spongy bone to compact bone.
What is Endochondral ossification?
It is where bone is preceded by a hyaline cartilage “model”, most bones develop this way.
What are the six stages of Endochondral ossification?
See notes: to much to list
Bone elongation
- The Ephiphyseal plate is a region of transition from cartilage to bone and functions as a growth zone where the bone elongated
- Metaphysis
The transitional zone facing the marrow cavity.
- Zones of metaphysis
- Zone of the reserve cartilage - resting cartilage.
- Zone of cell proliferation - chondrocytes multiplying.
- Zone of cell hypertrophy- chondrocytes enlarge.
- Zone of calcification- mineral deposition calcifies cartilage matrix.
- Zone of bone deposition - chondrocytes die, osteoblasts invade and deposit bone thus forming trabeculae.
More steps to bone elongation
- Osteoblasts deposit layer after layer of bone matrix converting spongy bone to compact bone.
- Growth in height occurs as the zone of reserve cartilage is continually pushed toward the ends of the bone.
- Achondroplastic dwarfism results from failure of cartilage growth in the long bone.
Bone widening and thickening
- Bones grow in diameter, and thickness throughout life.
2. Appositional growth is the deposition of new tissue at the surface.
Appositional growth
- Osteoblasts of the Periosteum deposit tissue on the bone surface, the tissue calcifies and the osteoblasts become trapped.
- Osteoclasts of the endosteum dissolve tissue on the inner bone surface widening the marrow cavity.
Three things about bone remodeling
- Bones are continually remodeled by absorption of old bone by osteoclasts and deposition by new osteoblasts.
- Wolff’s law of bone - architecture of the bone is determined by mechanical stresses placed upon it, the bone adapts to withstand those stresses.
- If a bone is heavily used or a stress is consistently applied, osteoblasts deposit new tissue and thickened bone.
Physiology of osseous tissue
What are the five factors?
- Mineral deposition and resorption
- Calcium homeostasis
- Hormones that balance calcium
- Phosphate homeostasis
- Other factors affecting bone
Mineral deposition
- A process in which calcium, phosphate, etc. are taken from the blood plasma and deposited in bone tissue.
Three facts of the mineral deposition process
- Osteoblasts lay down collagen fibers which become encrusted with Hydroxyapatite crystals that hard in the matrix.
- Most tissues have inhibitors to prevent calcification, but osteoblasts neutralize the inhibitors in bone.
- Ectopic ossification is abnormal calcification of tissue.
Mineral resorption
A process of dissolving bone
Three facts of the mineral resorption process
- Resorption is carried out by osteoclasts and releases minerals into the blood.
- Osteoclasts have receptors for calcium and respond to falling levels of calcium in the tissue fluid.
- Osteoclast secrete H+ and CL- follows forming HCl which dissolves the minerals and secretes acid phosphatase that digests collagen.
Physiology of osseous tissue
- Calcium homeostasis
- In addition to bone structure, calcium plays roles in communication among neurons, muscle contraction, blood clotting, and exocytosis.
- Phosphate groups are also components of DNA, RNA, ATP, phospholipids and other compounds.
- The skeleton is a reservoir in which these minerals are deposited and withdrawn.
- Changes in blood calcium concentration can have serious consequences including:Hypocalcemia which is a deficiency and causes excessive excitability of the nervous system and leads to muscle tremors,
spasms, or tetany.Hypercalcemia which means excessive nerve and muscle cells are less excitable causing depression of the nervous system, muscle weaknesses, sluggish reflexes and cardiac arrest.
Hormones that balance calcium
- Calcitriol which is a form of vitamin D.
- Calcitonin
- Parathyroid hormone or PTH
Calcitriol
- Using UV radiation the keratinocytes in the skin synthesize an inactive form of vitamin D which is converted to the active form.
Calcitonin
- Secreted from thyroid gland when blood calcium is too high.
- It lowers blood calcium levels by inhibiting osteoclast activity.
- Important in children, but has weak effects in adults.
Parathyroid hormone
- Secreted from the parathyroid glands when blood calcium is low.
- It raises blood CA 2+ levels by increasing bone resorption and kidney reabsorption, enhancing the effects of calcitriol, and inhibiting bone deposition.
Phosphate homeostasis
- Phosphate levels are not regulated as tightly as calcium.
2. Changes in plasma phosphate level are not associated with any disorder.
Other factors affecting bone
- At least 20 hormones, growth factors, and vitamins affect bone tissue.
- Bone growth is especially rapid and puberty when surges in growth hormone, estrogen and testosterone promote ossification.
- Sex steroids eventually deplete the cartilage of the epiphyseal plates and bring closure to the Epiphysis.
- Use of steroids by adolescent athletes can cause premature closure and result in abnormally short adult stature.
Bone disorders
Fractures and their repair
- There are stress fractures which are a break caused by abnormal trauma to a bone.
- Pathological fracture which is a break in a bone weekend by some other disease.
- Fractures are classified by a variety of characteristics.
Healing of fractures
4 types
- Hematoma formation and granulation of tissues- bleeding in the bone causes a clot to form. The clot is converted to granulation tissue by invasion of cells and blood capillaries.
- Soft callous formation- fibroblasts deposit collagen in the granulation tissue and chondroblasts produce Fibrocartilage.
- Hard callous formation- Osteoblasts deposit a bony collar around the fracture to unite the broken pieces.
- Bone remodeling- Osteoclasts remove fragments of bone while osteoblasts deposit spongy bone and then convert it to compact bone.
Ways to fix fractures
- Closed reduction- a procedure in which bone fragments are manipulated into their normal positions without surgery.
- Open reduction- surgical exposure of the bone and the use of plates, screws, or pins to realign the fragments.
Other bone disorders
- Rickets
Soft bones in children from vitamin D deficiency.
Osteomalacia
Soft bones in adults from vitamin D deficiency
Osteitis deformans or Paget’s disease
Excessive proliferation of osteoclasts with bone resorption and osteoblasts attempt to compensate by depositing extra bone.
Osteomyelitis
Inflammation of bone tissue and bone marrow as a result of the bacterial infection.
Osteogenesis imperfecta
A defect in collagen deposition that renders bones exceptionally brittle.
Osteosarcoma
Bone cancer most often in the tibia, Femur and humerus of males between 10 and 25 years old.
Osteoporosis
Severe loss of bone density resulting in brittle bones with increase of fractures especially in the hip, wrist, and vertebra.
What are 5 types of bone development
- Intramembraneous ossification
- Endochondral ossification
- Bone elongation
- Bone widening and thickening
- Bone remodeling
