Chpt. 7 & 8 Multiple Choice Created By Day

Osteoporosis affects more people than any other bone disease. Osteoporosis is a condition characterized by low bone density and deterioration of bone tissue, leading to an increased risk of fractures. It is more common in older adults, particularly women after menopause, but can affect people of all ages. The disease is often asymptomatic until a fracture occurs, making it a silent and widespread condition. Osteoporosis can be caused by various factors, including hormonal changes, inadequate calcium and vitamin D intake, sedentary lifestyle, and certain medical conditions or medications. Regular exercise, a balanced diet, and lifestyle modifications can help prevent or manage osteoporosis.

Yellow bone marrow is the correct answer because it does not contain myeloid tissue. Yellow bone marrow is primarily composed of adipose (fat) cells, while red bone marrow contains hematopoietic tissue responsible for the production of red and white blood cells. Myeloid tissue is a type of hematopoietic tissue found in red bone marrow, so it is not present in yellow bone marrow.

Wolff's law of bone states that bone remodels and adapts in response to mechanical stress. This means that when bone is subjected to increased stress or load, it will remodel itself to become stronger and more resistant to future stress. On the other hand, decreased stress or lack of mechanical loading can lead to bone loss or weakening. Therefore, Wolff's law explains the effect of mechanical stress on bone remodeling.

The correct sequence of events in the healing of a bone fracture starts with hematoma formation, which occurs when blood vessels are damaged, leading to the formation of a blood clot. This is followed by soft callus formation, where fibroblasts produce collagen to connect the broken bone ends. Next, hard callus formation takes place, which involves the deposition of minerals like calcium and the formation of a bony callus. Finally, bone remodeling occurs, where old bone tissue is replaced with new bone tissue, restoring the strength and structure of the fractured bone.

The expanded head at each end of a long bone is called an epiphysis. The epiphysis is responsible for the growth of the bone and contains the red bone marrow, which produces blood cells. It is covered with a layer of hyaline cartilage called articular cartilage, which helps reduce friction and absorb shock at the joint. The diaphysis refers to the shaft or main portion of the long bone. The periosteum is a tough, fibrous membrane that covers the outer surface of the bone.

The correct answer is periosteum; endosteum. The periosteum is a protective covering on the external surface of the bone, while the endosteum lines the internal surface of the bone.

Spicules and trabeculae are found in spongy bone. Spongy bone, also known as cancellous bone, is a type of bone tissue that has a porous, honeycomb-like structure. It is found at the ends of long bones, such as the femur and humerus, as well as in the interior of flat bones, such as the sternum and the bones of the skull. Spicules and trabeculae are thin, branching structures that make up the network of spongy bone. They provide support and help to distribute forces across the bone, making it stronger and more resistant to fractures.

In endochondral ossification, the precursor connective tissue is hyaline cartilage, which is replaced by bone. This process occurs during the development of long bones and involves the gradual replacement of the hyaline cartilage model with bone tissue. Initially, the embryonic mesenchyme differentiates into hyaline cartilage, which serves as a template for bone formation. As the bone grows, the cartilage is gradually replaced by bone cells, resulting in the formation of mature bone. This process is essential for skeletal development and growth.

Achondroplastic dwarfism is a hereditary condition characterized by abnormal bone growth. The epiphyseal plate, also known as the growth plate, is responsible for the elongation of long bones during childhood and adolescence. In individuals with achondroplastic dwarfism, the epiphyseal plate fails to function properly, resulting in shorter limbs. This condition affects the primary ossification center, where bone formation begins, but does not directly affect the secondary ossification center, bone marrow, or primary bone marrow. Therefore, the correct answer is the epiphyseal plate.

Blood Ca2+ deficiency stimulates parathyroid hormone secretion, which leads to increased osteoclast activity. Parathyroid hormone helps regulate calcium levels in the blood by stimulating the release of calcium from bones through the activity of osteoclasts. Osteoclasts break down bone tissue, releasing calcium into the bloodstream. This mechanism helps maintain calcium homeostasis in the body.

Osteoblasts are cells that are responsible for the formation of new bone tissue. When they become enclosed in lacunae, which are small cavities within the bone matrix, they differentiate into osteocytes. Osteocytes are mature bone cells that are found within the lacunae and are involved in maintaining the health and function of the bone tissue. Therefore, the correct answer is "osteoblasts; osteocytes".

Bone elongation is a result of cartilage growth. During growth, the cartilage at the ends of long bones, known as the growth plates, undergoes cell division and proliferation. This process, called endochondral ossification, leads to the formation of new bone tissue. As the cartilage cells divide and mature, they are gradually replaced by bone cells, resulting in bone elongation. This process is essential for the growth and development of the skeleton during childhood and adolescence.

The correct answer exemplifies a positive feedback process in bone mineral deposition because the first few crystals that form attract more calcium and phosphate. This means that as the crystals start to form, they create an environment that encourages more calcium and phosphate to be deposited, leading to further mineralization of the bone. This positive feedback loop promotes the growth and strengthening of the bone.

The correct answer is rickets; osteomalacia. Rickets is a condition that occurs in children when there is a deficiency of calcium and phosphate in the blood, leading to softness of the bones. Osteomalacia, on the other hand, is a similar condition that occurs in adults and is also characterized by softening of the bones due to low levels of calcium and phosphate. Both conditions are caused by a lack of proper mineralization in the bones and can lead to skeletal deformities and weakness.

An open fracture refers to a situation where the bone protrudes through the skin, exposing it to the external environment. This is in contrast to a closed fracture, where the bone does not break the skin. The terms complete and incomplete refer to the extent of the fracture line through the bone, while displaced indicates that the bone ends are not aligned properly. However, the specific term used to describe a fracture with bone protrusion through the skin is "open."

The skeleton is primarily responsible for providing support and protection to the body. It stores calcium and phosphate ions, which are important for maintaining bone density and strength. It also provides support for most muscles by serving as attachment points for them. Additionally, the skeleton protects vital organs such as the brain and spinal cord. However, it does not store red blood cells. These cells are produced in the bone marrow, but they are not stored within the skeleton itself.

Hydroxyapatite is an inorganic component of the bone matrix. It is a mineral form of calcium and phosphate that provides strength and rigidity to the bone structure. It helps to maintain the structural integrity of the bone and is responsible for its hardness. Proteoglycans, glycoproteins, collagen, and glycosaminoglycans are organic components of the bone matrix, but hydroxyapatite is the only inorganic component.

Chondrocytes, which are cells responsible for producing and maintaining cartilage, multiply in the zone of cell proliferation in the metaphysis. This zone is where chondrocytes undergo rapid cell division, leading to the growth and expansion of the cartilage tissue. The other zones mentioned in the options have different functions in the process of endochondral ossification, which is the process of cartilage turning into bone.

Resorption is the process of dissolving bone and returning its minerals to the bloodstream. This process is important for maintaining calcium and phosphate levels in the body. It occurs when osteoclasts, specialized cells in the bone, break down the bone tissue and release the minerals into the bloodstream. Resorption is a normal part of bone remodeling and allows for the removal of old or damaged bone tissue, as well as the release of minerals for use in other parts of the body.

Parathyroid hormone (PTH) is responsible for regulating the levels of calcium in the blood. It does so by stimulating osteoclast activity, which breaks down bone tissue to release calcium, and by promoting calcium reabsorption by the kidneys. However, PTH does not lower blood calcium levels. Instead, it increases blood calcium levels by releasing calcium from bone and increasing its reabsorption by the kidneys. Therefore, the correct answer is that PTH does not lower blood calcium.

Calcitriol is synthesized by the combined action of the skin, kidneys, and liver. It is important for the deposition of bone. Calcitriol is the active form of vitamin D and helps in the absorption of calcium and phosphorus from the intestines, which are essential for bone mineralization. It also regulates the levels of calcium and phosphorus in the blood, promoting bone growth and remodeling.

Hypocalcemia is a condition characterized by low levels of calcium in the blood. Calcium plays a crucial role in muscle function, and when levels are low, it can lead to muscle spasms. These spasms occur due to the impaired ability of calcium to regulate muscle contractions. Therefore, in the context of hypocalcemia, muscle weakness, sluggish reflexes, and spasms are all possible symptoms. Emotional disturbances and depression of the nervous system are not directly related to hypocalcemia and are not commonly associated with this condition.

A comminuted fracture is a type of fracture where the bone is broken into three or more pieces. This means that the bone has shattered into multiple fragments, rather than just being cracked or split. This type of fracture usually occurs due to a high-energy impact or force, such as a car accident or a fall from a significant height. Comminuted fractures are often more severe and require more complex treatment methods, such as surgery, to properly realign and stabilize the broken bone.

A pathologic fracture is a break in a bone weakened by some other disease. This means that the fracture occurs in a bone that has already been compromised by another condition, such as osteoporosis or cancer. Unlike a typical fracture caused by trauma, a pathologic fracture is more likely to occur with minimal force or even without any trauma at all. The weakened bone is unable to withstand normal stress and breaks easily. The healing time for a pathologic fracture can vary depending on the underlying disease and the individual's overall health.

During the healing process of a fracture, the initial stage involves the formation of a fracture hematoma, which is a blood clot that forms at the site of the fracture. This hematoma provides a foundation for further healing. As the healing progresses, granulation tissue forms, which is a type of connective tissue that helps in the formation of new blood vessels and provides a scaffold for the deposition of new bone. This granulation tissue is referred to as a soft callus. Eventually, the soft callus is replaced by a hard callus, which is a bony collar that forms around the fracture site. This hard callus provides stability and support to the healing bone.

Osteoblasts are bone-forming cells. They are responsible for the synthesis and secretion of the organic components of the bone matrix, which includes collagen and other proteins. Osteoblasts play a crucial role in bone formation and remodeling by laying down new bone tissue. They are derived from osteogenic (osteoprogenitor) cells and eventually become osteocytes, which are mature bone cells. Osteoclasts, on the other hand, are responsible for bone resorption, while osteons are structural units found in compact bone.

Osseous tissue is classified as connective tissue because it is composed of cells and an extracellular matrix that provides support and connects different parts of the body. Connective tissue is characterized by its ability to bind and support other tissues and organs. Osseous tissue, also known as bone tissue, is specialized connective tissue that forms the skeletal system and provides structural support, protection, and mineral storage for the body.

Yellow bone marrow is found in the marrow cavity of the diaphysis of an adult humerus. Yellow bone marrow is composed mainly of fat cells and is responsible for storing fat. It is found in the medullary cavity of long bones and helps to provide energy reserves for the body. In contrast, red bone marrow is responsible for producing blood cells and is found in the spongy bone of certain bones, such as the sternum, pelvis, and vertebrae.

Phosphate is an essential component of ATP, DNA, phospholipids, and RNA. ATP is the primary energy currency of cells, DNA carries genetic information, phospholipids are important for cell membrane structure, and RNA is involved in protein synthesis. However, phosphate is not directly involved in the formation of amino acids, which are the building blocks of proteins. Therefore, phosphate is necessary for all of the given options except amino acids.

Osteoclasts have a ruffled border with many deep infoldings of the plasma membrane, which allows them to resorb or break down bone tissue. On the other hand, osteocytes have long, thin, fingerlike cytoplasmic processes that extend through tiny channels called canaliculi. These processes allow osteocytes to communicate with each other and with other cells in the bone, as well as to receive nutrients and remove waste products. Therefore, the correct answer is "Osteoclasts; osteocytes."

Intramembranous ossification is a process where bone tissue is formed directly from mesenchymal cells, without the presence of a cartilage template. This type of ossification is responsible for the formation of flat bones, such as those found in the skull. Therefore, the correct answer is flat bones of the skull.

Appositional growth is the correct answer because it refers to the process by which bones increase in diameter throughout life. This occurs through the addition of new bone tissue on the outer surface of the existing bone, while the inner bone is resorbed. This process allows bones to adapt to mechanical stress and maintain their strength. Intramembranous ossification refers to the formation of bone within connective tissue membranes, while endochondral ossification involves the replacement of cartilage with bone. Interstitial growth is the process of bone lengthening, and metaphysical growth is not a recognized term in bone development.

Arteriosclerosis is a condition characterized by the abnormal calcification of a tissue, specifically the calcification of arteries. This calcification is not a normal process and can lead to the hardening and narrowing of the arteries, reducing blood flow and potentially causing various health issues. Ectopic ossification refers to the abnormal formation of bone in tissues where it is not normally found, and in the case of arteriosclerosis, it manifests as abnormal calcification rather than the formation of actual bone.

Osteoporosis is most common in elderly women because of the lack of estrogen, which would otherwise inhibit osteoclast activity. Estrogen plays a crucial role in maintaining bone density by suppressing the activity of osteoclasts, the cells responsible for breaking down bone tissue. As women age and their estrogen levels decline, osteoclast activity increases, leading to a net loss of bone density and an increased risk of osteoporosis.

The metaphysis is the correct answer because it is the area of the epiphyseal plate where bone replaces the hyaline cartilage in children and adolescents. The epiphyseal plate is a growth plate located at the ends of long bones, and it is responsible for bone growth. The metaphysis is the region between the epiphyseal plate and the diaphysis (shaft) of the bone, and it is where bone remodeling occurs. During bone growth, the cartilage in the epiphyseal plate is replaced by bone in the metaphysis, leading to an increase in bone length.

In a growing long bone, the epiphysis is the rounded end where the bone grows. The epiphysis is composed of articular cartilage, which is a smooth, slippery tissue that covers the ends of bones and helps reduce friction in joints. The epiphyseal plate is also present in the epiphysis and is a layer of cartilage that allows for longitudinal bone growth. As the bone grows, the cartilage in the epiphyseal plate is replaced by bone, forming the epiphyseal line. Therefore, the correct answer is articular cartilage and epiphyseal plate.

The given options are all types of tissues that can be found in a long bone. Osseous tissue refers to the bone tissue itself, while nervous tissue, adipose tissue, and cartilage are all present in various parts of a long bone, such as the periosteum, bone marrow, and articular cartilage respectively. Transitional epithelium, on the other hand, is not a tissue that is typically found in a long bone. It is a specialized type of epithelial tissue that lines organs such as the bladder and ureters, allowing them to stretch and accommodate changes in volume.

Central canals, also known as Haversian canals, are cylindrical channels found in compact bone. They contain blood vessels, nerves, and connective tissue. These canals are responsible for delivering oxygen, nutrients, and waste removal to and from the osteocytes (bone cells) within the compact bone. In contrast, spongy bone does not have a well-defined system of central canals, as it is composed of a network of irregularly arranged trabeculae with spaces between them. Therefore, central canals are common in compact bone but rarely seen in spongy bone.

Removal of the thyroid gland does not put women at risk of hypocalcemia. The thyroid gland is responsible for producing hormones that regulate calcium levels in the body. However, hypocalcemia is not directly caused by the removal of the thyroid gland. Hypocalcemia is a condition characterized by low levels of calcium in the blood, which can lead to various symptoms and complications. While removal of the thyroid gland may have other effects on the body, it does not directly impact calcium levels and therefore does not increase the risk of hypocalcemia.

A soft callus forms during the healing of a fracture. When a bone fractures, the body initiates a healing process where a soft callus is formed. This soft callus is made up of fibrous tissue and cartilage, and it helps stabilize the fractured bone. Over time, the soft callus is gradually replaced by a hard callus, which is composed of new bone tissue. This process is part of the remodeling phase of bone healing, where the bone gradually returns to its original strength and shape.

Hydroxyapatite and other minerals provide hardness to bones, while proteins provide some degree of flexibility. Hydroxyapatite is a mineral compound that makes up a large portion of the bone matrix, providing strength and rigidity. Other minerals, such as calcium phosphate, also contribute to the hardness of bones. On the other hand, proteins, such as collagen and elastic fibers, provide flexibility to bones, allowing them to withstand stress and absorb impact without breaking. Together, the combination of minerals and proteins gives bones their unique combination of strength and flexibility.

Osteoclasts are bone cells that are responsible for breaking down and resorbing bone tissue. They have a high number of lysosomes because lysosomes contain digestive enzymes that help in the breakdown of bone matrix. This allows osteoclasts to remove old or damaged bone tissue and make way for new bone growth. In contrast, osteoblasts are responsible for building new bone and have fewer lysosomes. Osteocytes are mature bone cells that are embedded within the bone matrix and have a limited number of lysosomes. Osteogenic cells and stem cells are precursor cells that can differentiate into osteoblasts, osteocytes, or other cell types and do not have as many lysosomes as osteoclasts.

Calcium is involved in various cellular processes, including muscle contraction, exocytosis, blood clotting, and communication among neurons. However, it does not directly participate in DNA synthesis. DNA synthesis primarily relies on enzymes and nucleotides, and while calcium may indirectly influence certain aspects of DNA replication, it is not a direct participant in the process.

Calcitriol is the active form of vitamin D and it plays a role in regulating calcium and phosphate levels in the body. It promotes intestinal absorption of calcium and decreases calcium excretion in the urine. It also increases osteoclast activity, which leads to bone resorption and release of calcium into the bloodstream. However, calcitriol does not directly affect cartilage growth in the epiphyseal plate. The growth of cartilage in the epiphyseal plate is primarily regulated by growth hormones and sex hormones.

If a thyroid tumor secretes an excessive amount of calcitonin, it would lead to an elevated level of osteoblast activity. Calcitonin is a hormone that helps regulate calcium levels in the blood. It inhibits osteoclast activity, which is responsible for breaking down bone tissue, and stimulates osteoblast activity, which is responsible for building new bone tissue. Therefore, an excess of calcitonin would result in increased osteoblast activity, leading to increased bone formation.