Chapter 6: Bone Tissue

At which point during embryonic development can most of the bones of the adult skeleton be identified?

16 weeks

Which is the last phase of endochondral ossification?

An epiphyseal cartilage separates the epiphysis from the diaphysis

As a fracture is repaired, new bone is added to the injury site. What term is used to describe the addition of new bone tissue? Identify which bone cell is responsible for this process and explain how it occurs.

Bone deposition, mineral deposition, or ossification are terms used to describe the process of adding new bone tissue to an injured or weak area. The cell that functions in this process is the osteoblast. This bone cell secretes both type I collagen fibers and osteoid ground substance via exocytosis. The osteoid ground substance will become hardened (ossified) with the addition of calcium and phosphorous.

What is responsible for appositional growth?

Bone is deposited by superficial osteoblasts.

In the final stage of bone repair, some of the osseous tissue must be broken down and removed. What term is used to define the breaking down of osseous tissue? Which bone cell would be best suited for this task?

Bone or mineral resorbtion is the term used to describe dissolving away osseous tissue. The osteoclast (bone breaker) secretes substances by exocytosis that dissolve the bone matrix.

Within days after a fracture, a "soft callus" of fibrocartilage forms. What fibers are found in this type of cartilage? Identify the cells required for fibrocartilaginous callus formation and list their functions.

Collagen fibers are found in high abundance in the fibrocartilage tissue matrix. Fibroblasts = produce collagen fibers that bridge the gaps between fracture ends Chondroblasts = secrete cartilage matrix

The extracellular matrix (ECM) of bone is considered to be a composite material made up of organic and inorganic matter. What makes up the organic and inorganic portions of the matrix? Describe the cellular mechanism involved in breaking down this matrix; include the bone cell required for the process.

Collagen fibers, glycosaminoglycans, and glycoproteins are organic while hydroxyapatite (crystallized calcium and phosphate) makes up most of the inorganic portion. Acid phosphates secreted by the osteoclast target the collagen fibers for destruction. The osteoclast has hydrogen pumps present in high numbers on the ruffled border. As hydrogen ions are pumped out they combine with chloride ions forming hydrochloric acid (HCl). The acid acts directly on hydroxyapatite to liberate calcium. Additionally HCL increases the solubility of calcium so it can be transferred back into the blood for other uses.

What type of bone growth is the doctor most likely looking for in the example above?

Endochondral ossification

Ectopic bones may occur in which of the following conditions?

Fibrodysplasia ossificans progressiva (FOP)

One way bones are classified is by their shape. How would you classify the bones fractured by Mrs. Morgan?

Flat, short, long, and irregular are the classifications of bones based on their shape. The patient's humerus is a long bone, while the occipital bone is flat, and the vertebra is an irregular bone.

Bill, age 15, is still growing, but his older sister Andrea, age 19, has stopped. What has changed in Andrea's bones?

Her epiphyseal plates have ossified.

Which condition, due to excessive cartilage formation at the epiphyseal cartilages, results in individuals who are very tall, with long, slender limbs?

Marfan syndrome

The body of Mrs. Morgan's vertebra is fractured. What type of bone tissue makes up the majority of the vertebral body? Describe the structure and function of this type of bone.

Most of the vertebral body is made up of spongy bone. The spongy bone is made up of trabeculae that have an open arrangement of osseous tissue, which shrinks the weight of bone. The spongy bone trabeculae align along stress lines to prevent damage.

Mrs. Morgan's fracture is described as having "bone tissue sticking out of the skin." This could make her susceptible to which of the following complications?

Osteomyelitis --- is the medical term for an infection in a bone; it can occur if an injury exposes the bone to germs.

All the following result in decreased calcium levels in the bloodstream EXCEPT __________. decreased PTH or calcitriol levels calcitonin inhibition of osteoclasts increased calcitonin levels PTH stimulation of osteoclasts

PTH stimulation of osteoclasts

Ankle fractures that affect both bones of the leg are called __________.

Pott's fractures

Which statement regarding the internal structure of long bone is correct?

The epiphysis consists largely of trabecular bone

The cartilage the doctor is referring to will disappear when

The osteoblasts work faster than cartilage producing cells

Most connective tissue, including bone, is highly vascular. Which anatomical structures in Mrs. Morgan's compact bone house blood vessels? What sign or symptom in Mrs. Morgan's case is directly related to disruption of these structures by her bone fractures? How is the sign or symptom related to these anatomical structures?

The perforating and central canals house arteries and veins plus nerves in compact bone. Mrs. Morgan is hemorrhaging as a result of her bones breaking. When bones break the jagged ends of the bones can pierce the blood vessels within the bone causing uncontrolled bleeding. Additionally the soft tissue (muscle, skin) surrounding the bone can be damaged resulting in further blood loss.

Which of the following statements regarding the homeostasis regulation of blood calcium is FALSE?

The three main organs that serve as the site for the regulation of blood calcium levels are the bones, the intestines, and the pancreas.

Define the following terms, used in the case and also in associated questions. a. hemorrhage b. fracture c. proximal d. diaphysis

a. hemorrhage- bleeding/abnormal blood flow. can be external like in this case since blood existed the body. b. fracture- crack or break due to trauma. in this case this fracture was an open or compound fracture because of the bone tissue sticking up out of her. c. proximal- near something relating to anatomy. the fracture of the left humerus was at the proximal diaphysis. d. diaphysis- the shaft that contains the medullary cavity. this is where the fracture took place of the left humerus, as the shaft is what received the fracture.

C cells of the thyroid gland secrete which of the following?

calcitonin

Which of the following hormones is currently thought to decrease plasma calcium levels in pregnant women and children?

calcitonin

PTH promotes the formation of which hormone?

calcitriol

Which hormone works directly in the intestine to increase plasma calcium levels?

calcitriol

Which substance accounts for almost two-thirds of the weight of bone?

calcium salts

During the early stages of endochondral ossification, which cells enlarge, then die and disintegrate?

chondrocytes

To form perforating fibers, osteoblasts from the cellular layer of the periosteum cement collagen fibers from tendons, ligaments, and joint capsules into which structures?

circumferential lamellae

The diaphysis of Mrs. Morgan's humerus is fractured. What type of bone makes up the majority of the diaphysis of long bones like the humerus? Describe the layers of bone tissue found here.

compact bone. • Concentric lamellae = circular shape; form the osteon • Interstitial lamellae = located in between the osteons • Circumferential lamellae = located at the outer/inner surfaces of compact bone

Which type of fracture occurs in vertebrae that are subjected to extreme stresses?

compression fractures

Osteoprogenitor cells are characterized by the following EXCEPT __________.

divide to produce daughter cells that differentiate into osteoclasts

Which bone is NOT formed via intramembranous ossification?

femur

Mrs. Morgan's fracture has not developed a soft callus. Which type of cartilage is her body having trouble forming?

fibrocartilage --- forms the soft callus, which appears just a few days after the fracture occurs.

Mrs. Morgan has an occipital bone fracture. Select the correct classification for this bone.

flat bone

Which of the following describes spiral fractures?

fractures that are produced by twisting stresses that spread along the length of the bone

What characteristic may cause life-threatening issues in individuals with Marfan syndrome?

genetic mutation that affects the structure of connective tissue throughout the body

A hard ossified bone in an adult actually begins within the embryo as a miniature version composed of __________.

hyaline cartilage

Which of the following would NOT be a way that parathyroid hormone (PTH) could alter plasma calcium levels? (Which one of the following is FALSE?) increase reabsorption of calcium in the kidney increase osteoclasts increase osteoblasts on bone

increase osteoblasts on bone

Remnants of osteons, which have been almost completely recycled by osteoclasts, are known as __________.

interstitial lamellae

All the following are characteristics of periosteum EXCEPT __________. it is an incomplete cellular layer that lines the medullary cavityit provides a route for the blood and nervous supplyit has two layers, an inner layer and an outer layerit actively participates in bone growth and repair

it is an incomplete cellular layer that lines the medullary cavity

Which organ prevents calcium loss in response to PTH stimulation?

kidneys

In intramembranous ossification, which cells first cluster together and start to secrete the organic components of the matrix?

mesenchymal cells

In what area of a long bone would it probably be easiest to observe the cartilage the orthopedic doctor refers to?

metaphysis

The periosteum contains all the following EXCEPT __________.

motor nerves

A depressed fracture is _______.

one in which broken bone fragments are displaced inward

Cells of the perichondrium need to take on a new role as ossification begins. They will become __________.

osteoblasts and begin to deposit bone matrix

At puberty, __________.

osteoblasts begin producing bone faster than chondrocytes are producing new epiphyseal cartilage

The process of osteolysis is performed by which cell population?

osteoclasts

Which component is NOT present in spongy bone?

osteons

Which class of bones develops inside tendons and is most commonly located near joints at the knees, the hands, and the feet?

sesamoid bones

One of Mrs. Morgan's fractures is described as being located on the proximal diaphysis. Which of these phrases best describes the anatomical location of this fracture?

shaft of the bone closest to the shoulder joint

What supplies the articular cartilage of long bones with oxygen and nutrients?

synovial fluid

As blood vessels extend into the spaces left by dying chondrocytes, the models begin to ossify internally. Where does internal ossification begin

the primary ossification center in the diaphysis

Which structural features of spongy bone are oriented along stress lines and are cross-braced extensively?

trabeculae

Which of the following is not a surface feature of the pelvis?

trochanter

Which surface feature is a smooth, grooved articular process shaped like a pulley?

trochlea