136 notecards = 46 pages (3 cards per page)
The Skeletal System
• Skeletal system includes:
Functions of the Skeletal System
Classification of Bones
• Bone are identified by:
1. Long bones
• Are long and thin
• Are thin with parallel surfaces
• Are small,irregular bones
• Have complex shapes
• Are small and thick
• Are small and flat
• Depressions or grooves:
Bone (Osseous) Tissue
• Dense, supportive connective tissue
Characteristics of Bone Tissue
• Dense matrix, containing:
• 2/3 of bone matrix is calcium phosphate, Ca3(PO4)2:
• 1/3 of bone matrix is protein fibers (collagen)
• Make up only 2% of bone mass:
• Mature bone cells that maintain the bone matrix
• Immature bone cells that secrete matrix compounds
• Matrix produced by osteoblasts, but not yet
• Mesenchymal stem cells that divide to produce
• Secrete acids and proteindigesting enzymes
• Bone building (by osteocytes) and bone recycling (by osteoclasts) must balance:
• The basic unit of mature compact bone
• Perpendicular to the central canal
• Lamellae wrapped around the long bone
• Does not have osteons
• The space between trabeculae is filled with red bone marrow:
• In some bones, spongy bone holds yellow bone marrow:
• The femur transfers weight from hip joint to knee joint:
Periosteum and Endosteum
• Compact bone is covered with membrane:
• Covers all bones:
• Collagen fibers of the periosteum:
• An incomplete cellular layer:
• Human bones grow until about age 25
• The process of depositing calcium salts
• The 2 main forms of ossification are:
• Also called dermal ossification:
Intramembranous Ossification: Step 1
• Mesenchymal cells aggregate:
Intramembranous Ossification: Step 2
• Blood vessels grow
IntramembranousOssification: Step 3
• Spongy bonedevelops and is remodeled into:
• Ossifies bones that originate as hyaline
Endochondral Ossification: Step 1
• Chondrocytes in the center of hyaline cartilage:
Endochondral Ossification: Step 2
• Blood vessels grow around the edges of the cartilage
Endochondral Ossification: Step 3
• Blood vessels enter the cartilage:
Endochondral Ossification: Step 5
• Capillaries and osteoblasts
Endochondral Ossification: Step 6
• Epiphyses fill with spongy bone:
Endochondral Ossification: Step 7
• As long as the epiphyseal cartilage continues to grow at its epiphyseal surface, the bone will continue to increase in length.
Bone Growth in Length
• Epiphyseal plate or cartilage growth plate
Zones of Growth in Epiphyseal Plate
• Zone of resting cartilage
Bone Growth in Width
• Only by appositional growth at the bone’s surface
• When long bone stops growing, after puberty:
• As long bone matures:
Blood Supply of Mature Bones
• 3 major sets of blood vessels develop
Lymph and Nerves
• The periosteum also contains:
• The adult skeleton:
Effects of Exercise on Bone
• Mineral recycling allows bones to adapt to stress
• Bone degenerates quickly
Effects of Hormones and Nutrition on Bone
• Normal bone growth and maintenance
• A dietary source of calcium and phosphate salts:
• Vitamin C is required for collagen synthesis,
• The hormone calcitriol:
• Growth hormone and thyroxine stimulate
Hormones for Bone Growth and Maintenance
The Skeleton as Calcium Reserve
• Bones store calcium and other minerals
Chemical Composition of Bone
Functions of Calcium
• Calcium ions are vital to:
• Calcium ions in body fluids:
Calcitonin and Parathyroid Hormone Control
Parathyroid Hormone (PTH)
• Low calcium ion levels in the blood cause the parathyroid glands in neck to secrete Parathyroid Hormone (PTH)
• High calcium ion levels in blood cause Calcitonin to be secreted by C cells (parafollicular cells) in thyroid
Fracture Repair: Step 1
Fracture Repair: Step 2
• Cells of the endosteum and periosteum:
Fracture Repair: Step 3
Fracture Repair: Step 4
• Osteoblasts and osteocytes remodel the fracture for up to a year:
- occurs at the ankle and affects both bones of the leg
- shatter the affected area into a multitude of bony fragments.
- break a bone shaft across its long axis
- twisting stresses that spread along the length of the bone
- produce new and abnormal bone arrangements, non-displaced fractures retain the normal alignment of the bones or fragments
- break in the distal portion of the radius (usually from reaching to cushion a fall)
- one side of the shaft is broken, and the other side is bent.
- where bone matrix is undergoing calcification and chondrocytes are dying. A clean transverse fracture along this line can generally heal well. Unless carefully treated, fractures between the epiphysis and the epiphyseal cartilage can permanently stop growth at this site.
- occur in the vertebrae subjected to extreme streses
Age and Bones
• Bones become thinner and weaker with age
Effects of Bone Loss
• The epiphyses, vertebrae, and jaws are most
• Severe bone loss
Hormones and Bone Loss
• Estrogens and androgens help maintain bone mass
Cancer and Bone Loss
• Cancerous tissues release osteoclastactivating
Name the five primary functions of the skeletal system. p170
The 5 primary functions of the skeletal system are: - support,
Identify the six broad categories for classifying a bone according to shape. p173
The 6 broad categories for classifying bones according to shape are:
Define bone marking. p173
A bone marking, (surface feature) is an area on the surface of a bone structured for a specific function, such as:
Mature bones cells are known as _____, bone-building cells are called __________, and ______ are bone-resorbing cells. p175
Mature bones cells are known as OSTEOCYTES, bone-building cells are called OSTEOBLASTS, and OSTEOCLASTS are bone-resorbing cells.
How would the compressive strength of a bone be affected if the ration of collagen to hydroxyapatite increased? p175
IF the ration of collagen to hydroxyapatite in a bone increased, the bone would become less strong (as well as more flexible.)
If the activity of osteoclasts exceeds the activity of osteoblasts in a bone, how will the mass of the bone be affected? p175
because osteoclasts break down or demineralize bone, the bone would have a reduced mineral content (less mass), as a result, it would be weaker.
Compare the structures and functions of compact bone and spongy bone. p179
Compact bone consists of osteons (Haversian systems) with little space between them. Compact bone lies over spongy bone and makes up most of the diaphysis. It functions to protect, support, and resist stress. Spongy bone consists of trabeculae with numerous red marrow-filled spaces. Spongy bone makes up most of the structure of short, flat, and irregular bones and is also found at the epiphyses of long bones. Spongy bone functions in storing marrow and providing some support.
A sample of bone has lamellae, which are not arranged in osteons, Is the sample most likely taken from the epiphysis or diaphysis? p179
The presence of lamellae that are not arranged in osteons is indicative of spongy bone, which is located in an epiphysis.
During intramembraneous ossification, which type of tissue is replaced by bone? p183
During intramembranous ossification, fibrous connective tissue is replaced by bone.
In endochondral ossification, what is the original source of osteoblasts? p183
In endochondral ossification, cells of the inner layer of the pericondrium differentiate into osteoblasts, and a cartilage model is gradually replaced by bone.
How could x-rays of the femur be used to determine whether a person has reached full height? p183
Long bones of the body, such as the femur, have an epiphyseal cartilage, a plate of cartilage that separates the epiphysis from the diaphysis so long as the bone is still growing lengthwise. An x-ray would indicate whether the epiphyseal cartilage is still present. If it is, growth is still occurring; if it is not, the bone has reached its adult length.
Describe bone remodeling. p184
Bone remodeling refers to the process whereby old bone is continuously being destroyed by osteoclasts while new bone is being constructed by osteoblasts.
Explain how heavy-metal ions could be incorporated into bone matrix. p184
The biochemistry of some heavy-metal ions, such as strontium, cobalt, uranium, and plutonium, is very similar to that of calcium. Osteoblasts cannot differentiate these abnormal heavy-metal ions from normal calcium ions, so the heavy metal ions become incorporated into the bone matrix. Over time, these dangerous ions can be released into circulation during normal bone remodeling.
Why would you expect the arm bones of a weight lifter to be thicker and heavier than those of a jogger? p186
The larger arm muscles of the weight lifter would apply more mechanical stress to the bones of the upper limbs. in response to that stress, the bones would grow thicker.
A child who enters puberty several years later than the average age is generally taller than average as an adult, Why? p186
Growth continues throughout childhood. At puberty, a growth spurt occurs and is followed by the closure of the epiphyseal cartilages. The later puberty begins, the taller the child will be when the growth spurt begins, so the taller the individual will be when growth is completed.
A 7yr old child has a pituitary gland tumor involving the cells that secrete growth hormone (GH), resulting in increased levels of GH. How will this condition affect the child's growth? p186
increased levels of growth hormone prior to puberty will result in excessive bone growth, making the individual taller.
Identify the hormones involved in stimulating and inhibiting the release of calcium ions from bone matrix. p188
Parathyroid hormone (PTH) influences osteoclast activity to cause a release of stored calcium ions from the bone. Under the influence of calcitonin, osteoclast activity is inhibited, while osteoblasts continue to lock calcium ions in the bone matrix. Therefore, PTH serves to increase blood calcium levels by causing its release from bone, and calcitonin decreases blood calcium levels by causing calcium to remain in bone.
Why does a child who has rickets have difficulty walking? p188
The bones of children who have rickets are poorly mineralized and as a resulte are quite flexible. under the weight of the bondy, the leg bones bend. The instability makes walking difficult and can lead to other problems of the legs and feet.
What effect would increased PTH secretion have on blood ion calcium levels? p188
Parathyroid hormone (PTH) stimulates osteoclasts to release calcium ions from bone and enhances calcitriol's effect on the intestinal absorption of calcium. Increase PTH secretion would result in an increase in the level of calcium ions in the blood.
How does calcitonin help lower the calcium ion concentration of blood? p188
Calcitonin lowers blood calcium levels by inhibiting osteoclast activity and increasing the rate of calcium excretion by the kidneys.
List the steps involved in fracture repair, beginning at the onset of the bone break. p192
Immediately following a fracture, extensive bleeding occurs at the site of injury. after several hours, a large blood clot called a fracture hematoma develops. Next, an internal callus forms as a network of spongy bone unties the inner edges, and an external callus of cartilage and bone stabilizes the outer edges. The cartilaginous external callus is eventually replaced by one, and the struts of spongy bone now unite the broken ends. With time, the swelling that initially marks the location of the fracture is remodeled, and little evidence that a break occurred remains.
At which point in fracture repair would you find an external callus? p192
An external callus forms early in the healing process, when cells from the endosteum and periosteum migrate to the area of the fracture. These cells form an enlarged collar (external Callus) that encircles the bone in the area of the fracture.
Define osteopenia. p193
Osteopenia is inadequate ossification and is common to the aging process. It results as a consequence of decreasing osteoblast activity accompanied with normal osteoclast activity.
Why is osteoporosis more common in older women that in older men? p193
In women, the sex hormones known as estrogens play an important role in moving calcium into bones. after menopause, the level of these hormones decreases dramatically; as a result, older women have difficulty replacing the calcium in bones that is being lost due to normal aging. In men, the level of sex hormones (androgens) does not decrease until much later in life.
Which of the following is NOT a function of the skeletal system?
The femur and the humerus are examples of __________.
The carpals or wrist bones are examples of __________.
What is the term for the extended tubular shaft of a long bone?
Which of the following types of cells are the mature bone cells that maintain the bone matrix?
Which of the following statements about bone tissue is FALSE?
It is made primarily of cells.
Which of the following types of bone cells is responsible for removing and recycling bone?
Which of the following are NOT structural components of compact bone?
Which component of bone is responsible for blood cell formation?
Red bone marrow
What is the name of the membrane that covers the outer surface of the bones?
Which of the following forms the flat bones of the skull?
In which of the following does bone replace existing cartilage?
Which of the following allows a bone to increase in diameter or width?
What is the term for the process in which the organic and mineral components of bone are continuously recycled and renewed?
Which of the following is an effect of stress on a bone?
The bone will become thicker.
Text: __________ is required for collagen synthesis, and a deficit results in a condition called scurvy.
Which two hormones play opposing roles in regulating the calcium level in blood and body fluids?
calcitonin and parathyroid hormone
Which of the following is the term for a fracture in which the broken bone breaks through the skin?
open or compound
Which of the following is the last step of fracture repair?
remodeling to return the bone to its normal shape
What is the term for a reduction in bone mass that is sufficiently large that it compromises the normal function of the bone?