Midterm 2 Anatomy and physiology (BI 331)

"The joint between mandibular condyle and mandibular fossa is functionally classified as _____ and structurally classified as ______."

-diarthrosis -synovial

"The growth plate between the epiphysis and diaphysis of a long bone is functionally classified as ______ and structurally classified as ______ "

-synarthrosis -cartilginous

"The Joint between the teeth and the jaw bone is functionally classified as ______ and structurally classified as _______ "

-synarthrosis -fibrous

"The calcified suture lines between flat skull bones is functionally classified as ______ and structurally classified as _______ "

-synarthrosis -fibrous

After a fracture, what is the correct sequence of repair for indirect bone healing? -Blood clot, bony patch, bone remodel, cartilage patch -Blood clot, bony patch, cartilage patch, bone remodel -Blood clot, cartilage patch, bony patch, bone remodel -Cartilage patch, blood clot, bony patch, bone remodel

Blood clot, cartilage patch, bony patch, bone remodel! Blood is always the first to arrive at an injury. After the fracture hematoma (blood clot) forms, a fibrocartilaginous callus (patch) forms. The cartilage is then replaced by a temporary bony callus. The bony callus is finally remodeled into mature bone.

Which of the following would be a symptom of severe lack of vitamin D in children aged 4-6? -High blood calcium -Being very tall -Narrow medullary cavities -Bowed lower limbs

Bowed lower limbs! Vitamin D is needed for absorption of calcium from the gut. People who do not have enough calcium (either by diet or lack of viitamin D) will have malformed bones. In particular, children will develop bowed legs because although they don't have calcium, they have collagen that makes their bones flexible, but not as supportive. Lack of vitamin D should not increase height, it might perhaps lower it due to reduced bone formation. Narrow medullary cavities result from excessive bone deposition at the endosteum. Again, without calcium this is hard to imagine. Without vitamin D, they cannot have high enough blood calcium - high blood calcium is almost always linked to excessive PTH.

What structures allow nutrients to reach trapped osteocytes (in either compact or spongy bone)? -Osteons -Trabeculae -Canaliculi -Lamellae

Canaliculi!

How do nutrients reach osteocytes trapped between lamellae of osteons? -diffusing from the central canal to the cells via canaliculi -diffusing from the central canal through the mineralized matrix -actively pumped from central canal through gap junctions in the osteocytes -it does not; the cells are dead an do not need nutrients

Diffusing from the central canal to the cells via canaliculi! As osteoblasts secrete their matrix, it mineralizes around them and they become trapped. Each lamella is a ring of osteoid secreted by osteocytes that eventually mineralizes and traps the osteocytes within pockets (lacunae). However, cytoplasmic processes of the osteocytes radiate out away from the lacunae and inhibit mineralization from filling in all the cracks between lamellae. Inside these cracks (called canaliculi), the osteocytes extend themselves and form gap junctions with their neighboring cells. The cells closest to the central canal receive the nutrients that diffuse out of the blood in the central canal and then allow them to diffuse outward through the connected cells within the canaliculi to the further and further osteocytes. These canaliculi are also useful for transmitting physical stress to through the bone, allowing bone to sense physical forces applied to bone and respond accordingly.

True or false? During formation of the mandible, the first osteoblasts to appear were delivered by blood vessels.

False! The mandible is formed by intramembranous bone formation. During intramembranous bone formation osteoblasts differentiate from mesenchyme cells before the arrival of blood vessels. This is in contrast to endochondral bone formation that requires blood vessels for successful action of osteoblasts.

In terms of functional properties, osteoid that fails to mineralize is likely most similar to: -fibrocartilage -bone marrow -skeletal muscle -endosteum

Fibrocartilage! Osteoid is unmineralized matrix of bone. Since the non-mineral part of the matrix is collagen, and fibrocartilage contains collagen, functionally speaking, of the ones listed here, osteoid would be most similar to fibrocartilage. Bone marrow does not contain collagen. Skeletal muscle does not contain collagen. The endosteum is a single layer thick of bone cells.

The __________ are joined to one another by __________ joints. -vertebral bodies; synarthrotic -paired flat skull bones; synchondrosis -femur and tibia; symphysis -flat hand bones (carpals); synovial

Flat hand bones (carpals); synovial! The carpals are joined to each other by synovial joints that allow much movement to type on a keyboard or click a mouse. When two bones are joined by fibrocartilaginous material, and not also synovial membranes inside an articular (joint) capsule, the joint is classified as a symphysis joint. It is a special case of the broader category of cartilaginous joints. Symphysis joints are usually amphiarthrotic because the fibrocartilage disc has some flexibility. The femur and tibia articulate at the knee, a diarthrotic synovial hinge joint. The flat bones of the skull are joined by fibrous suture joints - they are usually immobile and classified as synarthroses. Synchondroses joints are special cases of cartilaginous joints where the joining material is hyaline cartilage - they are usually synarthrotic (immobile).If you are unsure as to what these words all mean, you can use the tables in the joint chapter and pay special attention to the terms that start with the letters "syn."

Where do you find the cells that act to remodel or maintain bone? -In osteon lacunae -In the periosteum found covering bones -In the endosteum found lining the medullary cavity -Lining the central canal of the osteon -In all of the listed structures

In all of the listed structures! Bone is a dynamic tissue that remodels in response to stress and hormones. Osteoblasts and osteocytes act to build bone, an important feature of bone remodeling. Osteoclasts chew old bone and remove it from where it is not needed. Bone remodeling reshapes the bone while bone maintenance redeposits and renews old bone. The endosteum is a layer of osteoblasts, osteoclasts and osteoprogenitor cells that actively remodel bone. The endosteum is located in the central canal and covering all the trabeculae inside a bone. It is adjacent to the medullary cavity as well. The periosteum consists of the same cells (inner layer of periosteum) although it is located on the outside of bone, adjacent to the outermost compact bone. When bones get thicker or thinner, it is by both endosteal and periosteal deposition or removal. Osteocytes maintain the matrix and can act to build new bone. All the cells mentioned are found in the endosteum and periosteum, although only osteocytes are located in lacunae.

Where do you find a layer of osteoblasts, osteoclasts and osteogenic (osteoprogenitor) cells? -Covering the bony trabeculae -On the outer edge of bone -Inside the central canal of osteons -In all of these listed locations

In all of these listed locations!

Where do you find red bone marrow? -In the medullary (marrow) cavity -In the epiphysis, between the trabeculae

In the epiphysis, between the trabeculae!

In the growing 10 year old, the humerus becomes longer through ____ and wider through ____. -interstitial growth and endochondral bone formation; appositional growth at the periosteum -appositional growth and endochondral bone formation; appositional growth at the periosteum -interstitial growth and endochondral bone formation; interstitial growth at the periosteum -interstitial growth and intramembranous bone formation; appositional growth at the periosteum

Interstitial growth and endochondral bone formation; appositional growth at the periosteum! Bone elongates through interstitial growth of hyaline cartilage in the epiphyseal growth plate followed by replacement of that cartilage with bone (endochondral bone formation). At the edges of bones, appositional bone growth from the periosteum makes overall bone dimensions wider. Intramembranous bone formation does not occur in long bones.

Isometric vs isotonic contraction

Isometric: same-distance; not allow muscle to shorten (press on a wall; generate force but no movement) Isotonic: same-strength/same-afterload; move bone against constant weight/afterload

After a bone fracture, bone repair occurs. Depending on the severity of the break and the distance between the bone fragments, bone healing can occur in two ways: direct and indirect bone healing. With direct bone healing, the broken elements must be very close together and osteoblasts present at the site of injury deposit concentric lamellae around blood vessels. Indirect bone healing occurs when bone fragments are further apart. Initially, a large vascular response occurs, bringing cells and nutrients to the site of injury. Then, a temporary bridge (patch) forms. The temporary patch consists of cells and collagen fibers in a gelatinous, avascular matrix. The patch is then replaced by woven, trabecular bone but is later remodeled into mature bone. This type of bone repair can occur in spongy or compact bone and involves many cell types. Using the passage, during indirect and direct bone healing in the normal, healthy adult aged 40, which of the following would be recommended to help repair a fractured bone? -a drug that blocked the action of parathyroid hormone -a drug that blocked the action of calcitonin -limited exposure to sunlight -moderate weight bearing activity

Moderate weight bearing activity! During bone healing, you will want to promote osteoblast activity and bone remodeling. This means that you will want to have some activity and not inhibit any hormones needed for good bone health. Calcitonin and PTH have impacts on osteoblasts and osteoclasts, and unless they are out of balance, you would not want to interfere with their normal influence on bone. Since fracture repair involves remodeling as a normal part of the process, you will want activity of osteoblasts and osteoclasts. Vitamin D is needed for calcium absorption in the gut - exposure to sun light is needed for production of vitamin D. Again, you would not want to interfere with its normal activity.

Mature osseous connective tissue (bone) is composed of collagen fibers and mineralized matrix. When osseous CT is first made, the osteoblasts secrete osteoid onto which calcium salt then precipitates. What is osteoid? -Mostly collagen or collagen pre-cursors -Hydroxyapatite mineral -Hyaline cartilage -Mesenchyme

Mostly collagen or collagen pre-cursors! Osteoid is the immature bone that is first formed. It contains the collagen fibers and proteins that promote calcium salt formation onto the collagen.Hyaline cartilage is a different connective tissue that makes embryonic protoskeletons and articular cartilage. Mesenchyme is an embryonic connective tissue made of mesenchymal cells in a liquid ground substance. Hydroxyapatite mineral is the calcium salt that then forms on the osteoid.

What is the primary controller of blood calcium?

Parathyroid hormone

The skeletons of newborn children lack the bony processes where muscles attach, though they form in the first years of life. Which of the following best explains how and where these processes develop? -Periosteal osteoblasts are stimulated by physical stresses generated by tendons -Endosteal osteoclasts detect the location of tendons and secrete less acid -Tendons release growth hormone and calcitonin which activates nearby osteoblasts -Interstitial bone formation occurs in response to physical stresses generated by tendons

Periosteal osteoblasts are stimulated by physical stresses generated by tendons! Physical stress stimulates osteoblasts to deposit bone. Tendons attach at the periosteum. Increased physical stress at the periosteum stimulates the osteoblasts to make more bone at that site. Interstitial bone formation does not occur at the periosteum (site of tendon attachment); the endosteum is not where tendons attach; although it may seen popular to select that tendons release GH & calcitonin, this is not true - you should know that calcitonin is released by the thyroid gland.

What is the difference between spongy bone and compact bone -Spongy bone and compact bone are microscopically arranged differently -Spongy bone and compact bone are made of different matrix material -Spongy bone and compact bone contain different cellular populations -Spongy bone and compact bone are both absent in long bones.

Spongy bone and compact bone are microscopically arranged differently! Spongy bone and compact bone are made of the same matrix material (1/3rd collagen, 2/3rds mineral), contain the same cellular populations (osteoblasts, osteoclasts, osteocytes, osteoprogenitor cells) and are both found in long bones. Microscopically, the matrix arranges itself as osteons in compact bone, but as non-osteon, irregular lamellae of trabeculae in spongy bone.

In which of the following would you expect to find osteons? -The diaphyseal cortex of the humerus -The medullary (marrow) cavity of the femur -The trabeculae of the humeral distal epiphysis -The ligaments connecting adjacent vertebrae -The epithelium of the oral cavity

The diaphyseal cortex of the humerus! Osteons are the structural unit of compact bone. They make up the thick walls of long bone diaphyses and the most superficial compact bone collar (cortex) of long bone epiphyses. Compact bone is found in all bones with variable amounts of spongy bone between compact bone regions. Osteons do not exist in the ligaments of the neck (a dense regular connective tissue) or in epithelia. The medullary (marrow) cavities of long bones contain bone marrow (red or yellow, more likely yellow). Perhaps you selected the trabeculae within an epiphysis. Trabeculae are spongy bone struts. While spongy bone is made of the same material as compact bone, the organization is different and osteons do not form. It is important to remember the terms epiphysis and diaphysis - we will use them more when we talk about how bone grows.

In bones, a layer of osteoblasts and osteoclasts line the interior of the bone (this cellular layer covers all trabeculae, is adjacent to the medullary cavity and lines the inside of osteons). This layer is called the endosteum. What is its role in bone? -The endosteum can add or remove bone from the inside of bones, remodeling them. -The endosteum can add or remove cartilage from the inside of bones, replacing bone with cartilage. -The endosteum is an epithelial layer that protects the inside of bones and regulates transportation of nutrients to bones. -The endosteum has collagen fibers that anchor attaching muscles.

The endosteum can add or remove bone from the inside of bones, remodeling them! The endosteum is made of connective tissue cells (not epithelial cells) that can deposit or reabsorb bone from the internal aspect of the bone. During growth, the endosteum is particularly important to remodel bone from the inside. Without endosteal bone reabsorption, as bones grow wider overall, the bone would become too heavy. In other words, as bones grow wider (due to periosteal bone deposition), they maintain the same cortical bone thickness because of endosteal removal. Cartilage is deposited by chondroblasts. Muscles attach at the outside of bone on the fibrous layer of the periosteum.

In an infant's humerus, what happens if the rate of hyaline cartilage death is faster than the rate of cartilage interstitial growth? -The humerus would become too long at full maturity. -Nothing - this would not affect humerus development. -The humerus would become too short at full maturity.

The humerus would become too short at full maturity! The humerus is a long bone that grows through endochondral bone formation. During endochondral bone formation hyaline cartilage grows on one aspect of the epiphyseal plate (epiphyseal side) as it dies on the other (diaphyseal side). As it dies, it is degraded and replaced by bone. If the rate of growth is slower than the rate of death and replacement, the bone will replace the existing cartilage completely. Because bone is a hard tissue, it cannot grow from within (interstitial growth) to further elongate the bone and thus a long bone cannot grow any longer once the cartilage at the plate is gone. Too fast cartilage death is a problem in certain forms of dwarfism that results in smaller stature.

The periosteum is a double layered structure on the outside of all bones. The outermost layer is a fibrous connective tissue, the innermost layer (adjacent to the cortical bone) is a layer of osteoblasts, osteoclasts and osteogenic/osteoprogenitor cells. What are the two roles of the periosteum? -The outer fibrous layer attaches muscle; the inner cellular layer deposits or removes bone -The outer fibrous layer deposits or removes bone; the inner cellular layer attaches muscle -The outer fibrous layer makes the bone flexible; the inner cellular layer regulates nutrient/waste transfer -The outer fibrous layer regulates nutrient/waste transfer; the inner cellular layer makes the bone flexible

The outer fibrous layer attaches muscle; the inner cellular layer deposits or removes bone! The periosteum's outermost layer is a dense irregular connective tissue in which collagen fibers are oriented at varying angles (hence the name, dense - lots of fibers; irregular - fibers at many angles). This creates good tensile strength to resist the pull of the many muscles attaching at different angles. The collagen fibers in this layer blend with the fibers of muscle tendons and with the outermost compact bone. By blending together, the muscles attach very firmly to both the periosteum, which is then firmly anchored to the bone - it is more typical to tear a muscle in the middle of its belly than to tear it off the periosteum. The name of the connecting fibers between the periosteum and bone are called Sharpey's fibers. The cells of the inner periosteal layer are essential for bone remodeling. As bones grow in length, they need to add mass to the outer circumference of a bone and they need to be able to remove bone where it is not needed. Bone is alive and requires resources to maintain it. The periosteum helps balance the needs of the body for strong bones that are of the right construction for maximal efficiency of use.

Which of the following happens during formation of the ulna? -Cartilage cells are converted into osteoblasts -The outer periosteal bone forms before the inner spongy bone -The epiphyses ossify before the diaphysis -Osteoid deposition occurs before the appearance of blood vessels

The outer periosteal bone forms before the inner spongy bone! The ulna (like all long bones) forms via endochondral bone formation. During endochondral bone formation hyaline cartilage must die and be removed before osteoblasts can produce new bone on the remains of the cartilage. This bone deposition occurs at the outer edges of the structure to create a bony collar around the diaphysis. The osteoblasts depositing this bone must arrive via the invading blood vessel because cartilage cells cannot transform into bone cells. So, blood must precede bone in the case of endochondral bone formation. When long bones form, the diaphysis is the first site of bone formation. At birth, the diaphysis is usually bone but the epiphyses are still cartilage. The epiphyses ossify (creating secondary ossification sites) at different ages throughout childhood. The skeleton can be dated by the pattern of secondary ossification sites.

Once actin binding site is exposed, what happens between actin and myosin?

They interact with each other! Myosin head binds actin!

True or false? Bone mass (or bone density) is homeostatically regulated.

This is false. Although blood calcium is homeostatically regulated (via the parathyroid and thyroid glands the subsequent release of PTH or calcitonin), bone mass is not. In order to regulate blood calcium, these hormones will take bone mass or add bone mass to balance the blood. When the blood is balanced in terms of blood Ca2+, bone will be influenced by other factors (growth hormone, estrogen/testosterone, exercise, diet etc). But nothing is monitoring bone mass (or bone density) and then maintaining it within a narrow range - this is why we need to monitor it consciously as we age (through bone density tests or imaging). We know that bone mass may be in peril when we break a limb or have high metabolic demand for calcium (think about a lactating female), but do not use a receptor to monitor it, a control center to interpret the information and an effector to correct it. Therefore, bone mass (bone density) is not homeostatically regulated.

_____ are useful in the skeleton because they remodel most readily in response to stress and efficiently transmit forces while remaining lightweight. -trabeculae -osteons -cortical bone adjacent to periosteum -articular cartilages

Trabeculae! Trabeculae are the struts of spongy bone in the epiphyses and adjacent to the medullary cavity. They are more lightweight than dense compact bone (as evidenced by their many open spaces). In the epiphyses they transmit weight to the more dense compact bone of the diaphyseal cortex. They remodel very rapidly in response to signals (compressive stress/hormonal fluctuations); the proximal femoral spongy bone remodels every 3-6 months but the denser compact bone may take 3-7 years to fully remodel. Osteons are the structural unit of compact bone; compact bone comprises the bulk of the diaphyseal cortex (cortical bone) and the part adjacent to the periosteum. Articular cartilages (cartilage on the end of long bones) do not function for weight bearing as much as they function for friction reduction. They do not remodel in response to stress like spongy bone trabeculae do.

True or False? Spongy bone and compact bone are made of the same materials, but only compact bone has osteons.

True!

True or False? The sooner a person enters puberty, the sooner they will reach peak bone mass.

True! At the onset of puberty, cartilage and bone growth accelerate. However, cartilage death also accelerates (this effect is greater in females than males).

I think if a joint is more stable, it will.... -will be less likely to dislocate than a similar type, but less stable joint. -allow a greater range of movment than a similar type, but less stable joint. -bear less weight than a similar type, but less stable joint. -have less bony contact and supportive elements than a similar type, but less stable joint.

Will be less likely to dislocate than a similar type, but less stable joint. There is an inverse relationship between stability and mobility in joints. Meaning, if a joint is more stable, it likely has less range of movement. Stability of a joint comes from the structure of that joint - meaning, if the ligaments are tighter, the bony fit is more extensive or the muscles crossing a joint are stronger, the joint will be more stable. However, this will limit the mobility - think of a highly muscular person doing yoga - they usually are not terribly flexible. The more stable a joint, the less likely it is to dislocate (separate). Typically, in our body, because stability requires more material mass (more ligaments, more bone etc), they are metabolically more expensive than less stable joints. So, those joints that bear weight typically are more stable.

In vitamin C deficiency you cannot synthesize collagen. Which of the following would most likely occur? -Your skeleton would become malformed. -You would not be able to replenish lost epithelial cells. -You would not be able to sweat. -Your cartilage would become avascular.

Your skeleton would become malformed! The skeleton is constantly being degraded and replaced. Since the skeleton is 1/3rd collagen and 2/3rds mineral, an inability to make collagen would substantially affect the skeleton. Furthermore, proper collagen formation is required for proper bone mineral deposition. Epithelial cells do not have collagen. Sweat is mostly water and salt, and should not have collagen. Sweat glands are made of epithelial tissue, not lots of collagen like you would find in tendons/ligaments or bone. Cartilage is already avascular and actually secretes a compound that inhibits blood vessel formation. The best answer here is the one discussing skeleton formation.

Socket of shoulder joint

glenoid cavity