Biology Chapter 6: Skeletal System Overview

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Questions and Answers

What is the primary function of osteoblasts in bone tissue?

They sense mechanical strain on bones.

They break down bone tissue.

They form new bone tissue. (correct)

They maintain bone density.

In which type of ossification does mesenchymal tissue directly transform into bone?

Intramembranous ossification (correct)

Both endochondral and intramembranous ossification

Endochondral ossification

Appositional growth

What distinguishes spongy bone from compact bone?

Spongy bone is denser than compact bone.

Spongy bone contains more bone cells.

Spongy bone has a porous structure. (correct)

Spongy bone lacks blood vessels.

What classification of joint allows for the greatest range of motion?

Diarthrosis Signup and view all the answers

Which hormone is primarily responsible for increasing blood calcium levels?

Parathyroid hormone Signup and view all the answers

Which type of joint is exemplified by the connection between the vertebrae?

Cartilaginous Signup and view all the answers

How does appositional growth differ from interstitial growth in bones?

Appositional growth occurs at the surface; interstitial growth occurs within the bone. Signup and view all the answers

What are the two main types of proteins found in a sarcomere?

Contractile and regulatory proteins Signup and view all the answers

Which bone is the only movable facial bone in the human skull?

Mandible Signup and view all the answers

Which muscle fiber type is characterized by fatigue resistance and is used for endurance activities?

Type I fibers Signup and view all the answers

What type of bones are classified as 'floating' ribs?

Ribs that lack any anterior connection Signup and view all the answers

What is the primary role of ATP in the contraction cycle of skeletal muscle?

To energize myosin heads for muscle contraction Signup and view all the answers

What is the role of intervertebral discs?

To facilitate spinal movement and bear weight Signup and view all the answers

What is the term for the fixed point around which a lever rotates, often associated with muscle movement?

Fulcrum Signup and view all the answers

Which type of synovial joint allows for rotational movement around a single axis?

Pivot joint Signup and view all the answers

Which of the following best defines the antagonist muscle in a muscle pair?

Muscle that opposes the action of the prime mover Signup and view all the answers

Study Notes

Osteoblasts

Osteoblasts synthesize and secrete the organic matrix of bone, primarily collagen, which provides the framework for mineral deposition.
They play a key role in bone formation by initiating the process of bone mineralization through the deposition of calcium phosphate crystals onto the collagen matrix.

Intramembranous Ossification

In intramembranous ossification, mesenchymal tissue directly transforms into bone without the formation of a cartilaginous intermediate.
It is responsible for the formation of flat bones like the skull bones, clavicle, and some facial bones.

Spongy Bone vs. Compact Bone

Spongy Bone: Contains a network of trabeculae (thin struts of bone), creating a porous structure, is lighter and weaker than compact bone, and is found at the ends of long bones and in the interior of flat bones.
Compact Bone: Dense and solid, found on the outer surface of bones, provides strength and support, and contains Haversian canals that house blood vessels and nerves.

Synovial Joints

Synovial Joints: Characterized by a joint cavity filled with synovial fluid, which reduces friction and lubricates the joint.
Diarthroses (synovial joints) allow for the greatest range of motion, with examples including the shoulder, hip, and knee joints.

Blood Calcium Regulation

Parathyroid Hormone (PTH) is the primary hormone responsible for increasing blood calcium levels.
It stimulates osteoclasts to resorb bone, releasing calcium into the bloodstream, and also promotes resorption of calcium from the kidneys and intestines.

Vertebral Joints

The joints between vertebrae are classified as symphyses, which are characterized by fibrocartilaginous discs connecting bony surfaces.
These joints allow for limited movement and provide flexibility and support to the vertebral column.

Bone Growth

Appositional Growth: Occurs when new bone tissue is deposited on the surface of existing bone, increasing its width. It involves the activity of osteoblasts laying down new bone matrix on the periosteum.
Interstitial Growth: Occurs within the cartilage of growing bones, adding length to the bone. It relies on chondrocytes within the epiphyseal plates dividing and producing new cartilage matrix.

Sarcomere Proteins

Actin: Thin filaments that form the sliding component of the muscle contraction mechanism.
Myosin: Thick filaments that have "heads" that bind to actin filaments, initiating the sliding process.

Mandible

The mandible (lower jawbone) is the only movable facial bone in the human skull.

Slow-Twitch Muscle Fibers

Slow-Twitch Muscle Fibers: Primarily used for endurance activities, are fatigue-resistant, and rely heavily on oxidative metabolism to produce energy.

Floating Ribs

Floating Ribs: The 11th and 12th ribs are classified as floating ribs because they do not attach directly to the sternum (breastbone) through costal cartilages.

ATP in Muscle Contraction

ATP (adenosine triphosphate) powers the muscle contraction cycle.
It is required for myosin to detach from actin, re-energize for the next binding, and maintain the resting state of the sarcomere.

Intervertebral Discs

Intervertebral Discs: Act as shock absorbers between vertebrae, allow for limited movement, and contribute to the flexibility and support of the vertebral column.

Fulcrum

Fulcrum: The fixed point around which a lever rotates, often the joint where a muscle is attached to a bone.

Pivot Joints

Pivot Joints: Synovial joints that allow for rotational movement around a single axis.
Examples include the joint between the atlas (C1) and axis (C2) vertebrae in the neck, allowing for head rotation, and the joint between the radius and ulna bones in the forearm, enabling the hand to pronate and supinate.

Antagonist Muscle

Antagonist Muscle: The muscle that opposes the action of the agonist muscle in a pair.
For example, in the biceps and triceps pair, the triceps is the antagonist to the biceps, relaxing as the biceps contracts to bend the elbow.

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Description

This quiz covers essential concepts from Chapter 6 regarding the skeletal system. It includes the functions of bones, types of bone cells, and the anatomy of long bones, along with the processes of ossification and bone growth. Prepare to test your knowledge of both compact and spongy bone structures and their roles in maintaining health.