chapter 6 bones and skeletal tissue

In the red marrow of certain bones.

Triglycerides (fat).

Osteocalcin.

Axial skeleton and appendicular skeleton.

Bones of the skull, vertebral column, and rib cage.

To help us move from place to place and manipulate our environment.

As long, short, flat, or irregular.

The femur (thigh bone).

Bones that are roughly cube-shaped, such as those in the wrist and ankle.

Thin, flattened bones, such as the sternum and ribs.

Bones with complicated shapes that fit none of the preceding classes, such as vertebrae and hip bones.

Consists of compact bone sandwiching spongy bone.

Bone tissue, nervous tissue, cartilage, dense connective tissue, muscle, and epithelial tissues.

Gross, microscopic, and chemical levels.

Long bones, irregular bones, flat bones, and short bones.

Compact bone.

Spongy bone or trabecular bone.

Small needle-like or flat pieces that make up spongy bone.

Red or yellow bone marrow.

They consist of thin plates of spongy bone (diploë) covered by compact bone.

The periosteum covers the outside, and the endosteum covers the inside.

A typical long bone has a shaft (diaphysis), bone ends (epiphyses), and membranes.

The diaphysis is the tubular shaft that forms the long axis of the bone, constructed of compact bone surrounding a central medullary cavity.

The medullary cavity contains yellow marrow (fat) in adults.

The epiphysis is the bone end, consisting of an outer shell of compact bone and an interior of spongy bone.

Articular cartilage cushions the opposing bone ends during movement and absorbs stress.

The epiphyseal line is a remnant of the epiphyseal plate, which is a disc of hyaline cartilage that grows during childhood to lengthen the bone.

The periosteum is a double-layered membrane that covers the external surface of the entire bone except the joint surfaces.

The inner osteogenic layer contains osteoprogenitor cells, osteoclasts, and osteoblasts.

The endosteum is a delicate connective tissue membrane that covers internal bone surfaces, including the trabeculae of spongy bone and the canals in compact bone.

Unlike cartilage, bones are well vascularized, with main vessels serving the diaphysis being a nutrient artery and a nutrient vein.

Osteoclasts are bone-resorbing cells that break down bone tissue.

Before age 40.

About 3%.

A virus may trigger it, although the exact cause is unknown.

Bisphosphonates and calcitonin.

Bone formation exceeds bone resorption.

These processes are in balance.

Bone resorption predominates.

By 8 weeks after conception.

The epiphyseal plates.

Poorer circulation can lead to longer healing times for fractures in elderly people.

Daily ultrasound treatments or electrical stimulation of fracture sites.

A fracture where the bone is broken into three or more pieces, particularly common in aged individuals whose bones are more brittle.

A compression fracture occurs when a bone is crushed, commonly seen in porous bones like osteoporotic bones subjected to extreme trauma, such as a fall.

A spiral fracture is a ragged break that occurs when excessive twisting forces are applied to a bone, commonly seen in sports injuries.

In an epiphyseal fracture, the epiphysis separates from the diaphysis along the epiphyseal plate, often occurring where cartilage cells are dying and calcification is happening.

A depressed fracture is when a broken bone portion is pressed inward, typically associated with skull fractures.

A greenstick fracture is an incomplete break where one side of the bone shaft breaks while the other side bends, common in children due to their more flexible bones.

Osteomalacia is characterized by poorly mineralized bones that are soft and weak due to inadequate calcium salt deposition.

Rickets is the analogous disease to osteomalacia in children, causing more severe symptoms due to rapid bone growth, leading to bowed legs and deformities.

They are caused by insufficient calcium in the diet or a vitamin D deficiency.

Osteoporosis is a disease where bone resorption outpaces bone deposit, leading to a decline in bone mass and increased fragility.

Risk factors include decreased sex hormones, insufficient bone stress, poor diet, smoking, genetics, hormone-related conditions, and certain medications.

Osteoporosis can be prevented by maintaining a healthy diet, engaging in weight-bearing exercise, and treated with medications like bisphosphonates and denosumab.

Estrogen helps restrain osteoclasts and promotes new bone deposit; its decrease after menopause is strongly implicated in osteoporosis in older women.

Common fracture sites include compression fractures of the vertebrae and fractures of the neck of the femur (broken hip).

Increasing vitamin D intake and sunlight exposure usually cures osteomalacia and rickets by promoting calcium absorption and bone mineralization.

Excessive and haphazard bone deposit and resorption, leading to weak, poorly mineralized bone.

Pagetic bone.

The spine, pelvis, femur, and skull.

Central canals (Haversian canals) and perforating canals (Volkmann's canals).

Canaliculi connect osteocytes to each other and to the central canal, allowing for communication and nutrient exchange.

Incomplete lamellae that fill gaps between intact osteons or are remnants of osteons cut through by remodeling.

Lamellae that extend around the entire circumference of the diaphysis, helping to resist twisting of the long bone.

Spongy bone has trabeculae that align along lines of stress and contains irregularly arranged lamellae and osteocytes, with no osteons present.

Bone contains both organic components (cells and osteoid) and inorganic components (mineral salts).

They allow bone to resist tension (stretch).

They allow bone to resist compression.

Healthy bone is half as strong as steel in resisting compression and fully as strong as steel in resisting tension.

It contains blood vessels and nerves that supply the bone.

Structural units of compact bone that consist of a central canal surrounded by concentric layers of lamellae.

Canaliculi are small channels that connect lacunae and allow for communication and nutrient exchange between osteocytes.

Osteocytes are mature bone cells that maintain bone tissue and communicate with other bone cells.

Bones and cartilages.

Bones perform various functions including support, protection, movement, and mineral storage.

Bones are classified based on their shape and structure.

Bones develop through processes such as ossification and growth.

Bone remodeling is the process of bone tissue being formed and reshaped throughout life.

Bone repair involves processes that restore the integrity of bone after injury.

Bones are often thought to be lifeless, but they are actually living, dynamic organs.

Cartilages provide resilience and support within the skeletal system.

Hyaline, elastic, and fibrocartilage.

Water.

The perichondrium.

Hyaline cartilage.

Articular cartilages, costal cartilages, respiratory cartilages, and nasal cartilages.

The external ear and the epiglottis.

It is highly compressible with great tensile strength.

Appositional growth and interstitial growth.

Cartilage-forming cells in the perichondrium secrete new matrix against the external face of existing cartilage.

Lacunae-bound chondrocytes divide and secrete new matrix, expanding the cartilage from within.

Calcified cartilage is not bone; they are always distinct tissues.

Chondroblasts.

Cartilage has a flexible extracellular matrix, while bone has a rigid extracellular matrix due to inorganic calcium salts.

The Axial skeleton and the Appendicular skeleton.

By age 25, nearly all bones are completely ossified and skeletal growth ceases.

The digestive system provides nutrients needed for bone health and growth.

Mineral storage, blood cell formation, triglyceride storage, and hormone production.

Fused bones of the skull protect the brain, vertebrae surround the spinal cord, and the rib cage protects vital organs of the thorax.

Skeletal muscles attach to bones by tendons and use bones as levers to move the body and its parts.

Support, Protection, Anchorage, Movement, Mineral storage, Blood cell production, and Energy storage.

Calcium and phosphate.

Bones provide a framework that supports the body and cradles its soft organs.

Hematopoietic tissue, also called red marrow, is responsible for blood formation and is found in different locations in infants and adults.

Red bone marrow.

Much of the red marrow is replaced by yellow marrow.

In the cavities between trabeculae of spongy bones.

If a person becomes very anemic and needs more red blood cells.

(1) Projections for muscle and ligament attachment, (2) surfaces that form joints, (3) depressions and openings for blood vessels and nerves.

Flat bones like the sternum and some irregular bones like the hip bone.

They provide information about how bones and attached muscles and ligaments work together.

It covers the external surface of the diaphysis.

Hyaline cartilage.

A large rounded projection that may be roughened.

A narrow ridge of bone that is usually prominent.

A very large, blunt, irregularly shaped process, with examples found only on the femur.

A narrow ridge of bone that is less prominent than a crest.

A small rounded projection or process.

A raised area on or above a condyle.

A sharp, slender, often pointed projection.

A bony expansion carried on a narrow neck.

A smooth, nearly flat articular (joint) surface.

A rounded articular projection that often articulates with a corresponding fossa.

A furrow that serves as a depression.

A narrow, slitlike opening.

A canal-like passageway.

A cavity within a bone, filled with air and lined with mucous membrane.

Osteoprogenitor cells, osteoblasts, osteocytes, bone lining cells, and osteoclasts.

They resorb (break down) bone as part of the remodeling process.

In the membranous periosteum and endosteum.

They make bone a dynamic living tissue by continuously resorbing and depositing bone.

Osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts.

They are stem cells that can differentiate into osteoblasts or persist as osteoprogenitor cells.

Osteoblasts are matrix-synthesizing cells responsible for bone growth.

Osteocytes monitor and maintain the mineralized bone matrix and act as stress sensors.

Bone lining cells are flattened cells that help maintain the bone matrix where remodeling is not occurring.

The osteon, or Haversian system.

The ruffled border increases the surface area for enzymatically degrading bone and seals off the area from surrounding matrix.

They communicate mechanical stress information to osteoblasts and osteoclasts for bone remodeling.

It includes collagen and calcium-binding proteins, making up the osteoid.

A group of hollow tubes of bone matrix called lamellae, with a central canal containing blood vessels and nerve fibers.

Collagen fibers in a particular lamella run in a single direction, while those in adjacent lamellae run in different directions.

It helps to withstand torsional stresses and resist twisting.

Collagen provides flexibility and tensile strength, allowing bones to resist stretching and twisting.

They are bonds in or between collagen molecules that stretch and break on impact, dissipating energy to prevent fractures.

65% by mass consists of inorganic hydroxyapatites or mineral salts.

The organic components include collagen and other fibers secreted by osteoblasts, contributing to bone structure and resilience.

They are present as tiny, tightly packed, needle-like crystals in and around collagen fibers in the extracellular matrix, contributing to the exceptional hardness of bone.

Bones provide an enduring 'monument' that reveals the shapes, sizes, and ailments of ancient peoples.

Intramembranous ossification and endochondral ossification.

Ossification is the process of bone tissue formation, leading to the formation of the bony skeleton in embryos and continuing as bone growth until early adulthood.

Endochondral ossification involves replacing hyaline cartilage with bone, while intramembranous ossification involves developing bone from a fibrous membrane.

Epiphyseal plates allow long bones to grow by accommodating mitosis during development.

The hyaline cartilage is broken down as ossification proceeds, serving as a model for bone construction.

A bone collar forms around the diaphysis of the hyaline cartilage model.

Chondrocytes hypertrophy, calcify the surrounding cartilage matrix, die, and lead to the deterioration of the matrix, opening up cavities.

The area where chondrocytes within the shaft hypertrophy and the bone collar forms around the diaphysis.

The bone collar forms around the diaphysis of the hyaline cartilage model.

The cartilage calcifies and then develops cavities.

The periosteal bud invades the internal cavities and spongy bone forms.

A medullary cavity forms and secondary ossification centers appear in the epiphyses.

Hyaline cartilage remains only in the epiphyseal plates and articular cartilages.

Secondary ossification centers develop, typically resulting in spongy bone without a medullary cavity.

It is formed as osteoclasts break down newly formed spongy bone in the center of the diaphysis.

It allows for the elongation of the bone by facilitating the division of viable cartilage cells.

Osteoclasts break down the newly formed spongy bone to create the medullary cavity.

It is the area where bone formation begins in the diaphysis of a long bone.

Cranial bones of the skull (frontal, parietal, occipital, and temporal bones) and the clavicles.

Around week 8 of development.

Long bones lengthen by interstitial growth of the epiphyseal plate cartilage and grow in thickness by appositional growth.

It allows for the growth of long bones by providing a region for cartilage growth that is replaced by bone.

Proliferation zone, Hypertrophic zone, Calcification zone, Ossification zone.

Cells divide quickly, pushing the epiphysis away from the diaphysis and lengthening the long bone.

Older chondrocytes enlarge, their lacunae erode, leaving large interconnecting spaces.

The surrounding cartilage matrix calcifies, chondrocytes die, and blood vessels invade, leading to the formation of calcified cartilage spicules.

Calcified spicules are invaded by marrow elements, osteoclasts erode them, and osteoblasts cover them with new bone, ultimately forming spongy bone.

The rate of cartilage growth on the epiphysis-facing side is balanced by its replacement with bony tissue on the diaphysis-facing side.

Resting zone, Proliferation zone, Hypertrophic zone, Calcification zone, Ossification zone.

Cartilage cells undergo mitosis.

Older cartilage cells enlarge.

Matrix becomes calcified; cartilage cells die; matrix begins deteriorating.

New bone is forming.

The chondroblasts divide less often, and the plates become thinner until replaced by bone tissue.

It is the process where the epiphyseal plates are entirely replaced by bone tissue, occurring at about 18 years in females and 21 years in males.

Bones widen as they lengthen through appositional growth, where osteoblasts secrete bone matrix on the external surface.

Osteoclasts remove bone on the endosteal surface of the diaphysis.

It produces a thicker, stronger bone while preventing it from becoming too heavy.

Growth hormone released by the anterior pituitary gland.

They modulate the activity of growth hormone, ensuring proper proportions of the skeleton as it grows.

Estrogen levels increase, stimulating the growth spurt and later inducing epiphyseal closure, ending longitudinal bone growth.

It results in excessive height, known as gigantism.

They can produce characteristic types of dwarfism.

Bone remodeling involves bone deposition and removal, replacing about 5-10% of our skeleton each year to prevent brittleness and fractures.

Osteoblasts, osteocytes, and osteoclasts.

Spongy bone is replaced every three to four years, while compact bone is replaced every 10 years or so.

They break down the bone matrix by digging depressions, secreting acid and enzymes to dissolve minerals and digest the organic matrix.

They deposit new bone matrix, starting as an osteoid seam that becomes calcified.

The binding of calcium ions by osteoid proteins raises local concentrations of calcium and phosphate, leading to crystal formation.

One maintains Ca2+ homeostasis and the other keeps bone strong in response to mechanical and gravitational forces.

It is essential for maintaining the resting membrane potential of all cells, allowing nerves to fire and muscles to contract.

Severe neuromuscular problems.

Hypocalcemia, which causes hyperexcitability.

Hypercalcemia, which causes nonresponsiveness and inability to function.

Formation of kidney stones or undesirable deposits of calcium salts in other organs.

1200-1400 g.

In bone minerals.

They use calcium in bone as a storage bank for resorption or deposits to maintain extracellular fluid calcium levels.

9-11 mg per dl (100 ml) of blood.

Parathyroid hormone (PTH).

PTH is released, stimulating osteoclasts to resorb bone and release Ca2+ into the blood.

Its effects are negligible at normal levels but can lower blood calcium levels temporarily at pharmacological doses.

A bone grows or remodels in response to the demands placed on it.

The common stresses it encounters.

It tends to bend, compressing the bone.

Mechanical stress causes the compact bone of long bones to be thickest midway along the diaphysis, where bending stresses are greatest.

Wolff's law explains that bones adapt to the stresses placed on them, resulting in thicker bones in more used limbs and curved bones being thickest where they are most likely to buckle.

Deforming bone pushes fluid containing ions through the canaliculi, creating an electrical current that osteocytes detect, leading to the release of chemical messengers promoting bone formation.

Hormonal controls determine whether and when remodeling occurs, while mechanical stress determines where remodeling occurs.

Bone mass will decrease.

Bone repair involves hematoma and callus formation, followed by remodeling.

Thinner and weaker bones.

The lack of mechanical stress in a microgravity environment leads to bone thinning and weakening.

Nondisplaced fractures (normal position) and displaced fractures (out of alignment).

A complete fracture is when the bone is broken through.

An open fracture penetrates the skin, while a closed fracture does not.

A hematoma forms at the fracture site due to torn blood vessels.

Fibrocartilaginous callus forms as fibroblasts and chondroblasts invade the fracture site and produce collagen and a cartilaginous matrix.

A bony callus forms as osteoblasts create spongy bone within the fibrocartilaginous callus.

Bone remodeling occurs, where excess material is removed and compact bone is laid down to reconstruct the shaft walls.

Six to eight weeks.

It helps determine the tendency to accumulate bone mass during early life and a person's risk of osteoporosis later in life.

Bone mass decreases with age, starting in the fourth decade, except for the bones of the skull.

Skeletal mass is generally greater in males than in females.

A congenital condition involving defective cartilage and endochondral bone growth, resulting in short limbs but normal-sized membrane bones; a type of dwarfism.

Pain in a bone.

Inflammation of bony tissue.

A disorder in which the bone matrix contains inadequate collagen, putting it at risk for shattering; also known as brittle bone disease.

Inflammation of bone and bone marrow caused by pus-forming bacteria, commonly affecting long bones and causing acute pain and fever.

Hyaline, elastic, and fibrocartilage.

Bones give the body shape, protect and support organs, provide levers for muscles, store minerals, and produce blood cells.

Bones are classified by their location (axial or appendicular) and shape (long, short, flat, or irregular).

A long bone consists of a diaphysis (shaft) and epiphyses (ends), with a medullary cavity containing yellow marrow and spongy bone in the epiphyses.

Bone markings are important anatomical landmarks that reveal sites of muscle attachment, points of articulation, and sites of blood vessel and nerve passage.

The skeletal system provides support for body organs including the skin.

The skin provides vitamin D needed for proper calcium absorption and use.

The skeletal system provides levers plus ionic calcium for muscle activity.

Muscle pull on bones increases bone strength and viability; helps determine bone shape.

The skeletal system protects the brain and spinal cord; provides a depot for calcium ions needed for neural function.

Nerves innervate bone and joint capsules, providing for pain and joint sense.

The skeletal system provides some bony protection; stores calcium needed for second-messenger signaling mechanisms.

Hormones regulate uptake and release of calcium from bone; promote long bone growth and maturation.

Bone marrow cavities provide a site for blood cell formation; matrix stores calcium needed for cardiac muscle activity.

The cardiovascular system delivers nutrients and oxygen to bones; carries away wastes.

The skeletal system provides some protection to lymphatic organs; bone marrow is the site of origin for lymphocytes involved in immune response.

Lymphatic vessels pick up leaked plasma fluids and proteins from the periostea; immune cells protect against pathogens.

The skeletal system protects lungs by enclosure (rib cage).

The respiratory system provides oxygen; disposes of carbon dioxide.

The skeletal system provides some bony protection to intestines, pelvic organs, and liver.

The skeletal system protects pelvic organs (urinary bladder, etc.).

Kidneys activate vitamin D; dispose of nitrogenous wastes.

The skeletal system protects some reproductive organs by enclosure.

Gonads produce hormones that influence the form of the skeleton and epiphyseal closure.

Osteoprogenitor cells, osteoblasts, osteocytes, bone lining cells, and osteoclasts.

The osteon.

A central canal surrounded by concentric lamellae of bone matrix.

They maintain the bone matrix.

It includes osteoid and hydroxyapatites (calcium salts).

By endochondral ossification of a hyaline cartilage model.

The clavicles and most skull bones.

By interstitial growth of the epiphyseal plate cartilage and its replacement by bone.

It increases bone diameter/thickness.

The process involving bone deposition and removal in response to hormonal and mechanical stimuli.

PTH is released, stimulating osteoclasts to digest bone matrix and release ionic calcium.

Formation of a hematoma, a fibrocartilaginous callus, a bony callus, and bone remodeling.

Inadequate mineralization of bones, often due to inadequate vitamin D.

Bone breakdown outpaces bone formation, leading to weak and porous bones.

The shape of a bone being determined by mechanical stresses placed on it.

The predictable and precisely timed process of bone formation.

It remains fairly constant, but begins to decline in the 30s as resorption exceeds formation.

Greenstick fracture.

Osteoporosis.

The process involves the formation of a cartilage model, followed by the invasion of blood vessels, osteoblasts replacing cartilage with bone, and the formation of the medullary cavity.

Short bone.

They receive nutrients through canaliculi that connect them to the blood vessels.

Because bone remodeling occurs, maintaining the thickness while allowing for growth in diameter.

It involves the formation of an osteoid seam followed by the calcification front where minerals are deposited.

During childhood and adolescence.

Due to decreased bone density and strength associated with aging.

Because children's bones are more flexible and less brittle than adult bones.

It is taken from the diaphysis, as it shows concentric layers surrounding a central cavity.

Due to lack of mechanical stress and weight-bearing activity, which are essential for bone maintenance.

Bone is less resilient than cartilage, has a slower regeneration rate, and has better access to nutrients due to its vascularity.

Hormones regulate calcium levels and bone density, while mechanical forces stimulate bone formation and remodeling based on stress.

The child likely has rickets due to vitamin D deficiency, which affects bone mineralization.

It would be more prone to deformities and fractures due to lack of adaptation to stress and strain.

He experienced a serious injury where the end of his upper arm bone was starting to twist off due to excessive stress.

She has a compound fracture due to the bone protruding through the skin.

Infection.

Her leg healing will involve laying down cartilage in the injured area, followed by bone.

Approximately 6 to 8 weeks, but complications may arise due to the damaged nutrient artery.

The statement 'The only supplement I should need would be calcium' indicates a lack of understanding of the importance of vitamin D.

It is unlikely to fully regenerate due to the limited regenerative capacity of cartilage and the extent of the injury.