Which of the following is not a synovial joint?
Hinge
Ball-and-socket
Symphysis
Pivot
The Correct Answer is C
Joints are classified based on their structure and the degree of movement they allow. Synovial joints are the most mobile type of joint in the body and are characterized by a synovial cavity, articular cartilage, and a joint capsule filled with synovial fluid. Examples include hinge, ball-and-socket, and pivot joints. In contrast, some joints are cartilaginous, where bones are united by cartilage and movement is limited. Understanding these classifications is essential for distinguishing joint anatomy and function.
A. Hinge: hinge joints are synovial joints. They allow movement in one plane, typically flexion and extension, like the elbow or interphalangeal joints. They are characterized by a synovial cavity and articular cartilage that reduce friction during movement. Therefore, hinge joints are a type of synovial joint.
B. Ball-and-socket: ball-and-socket joints are synovial joints that allow multiaxial movement, including flexion, extension, abduction, adduction, and rotation. Examples include the shoulder and hip joints. They are highly mobile due to the spherical head of one bone fitting into a cup-shaped socket. Therefore, they are classified as synovial joints.
C. Symphysis: symphysis joints are cartilaginous joints, not synovial joints. In a symphysis, bones are joined by fibrocartilage, which allows limited movement and provides strength and shock absorption. Examples include the pubic symphysis and intervertebral discs. Since they lack a synovial cavity and synovial fluid, they are not synovial joints.
D. Pivot: pivot joints are synovial joints that allow rotational movement around a single axis. A classic example is the atlantoaxial joint between the first and second cervical vertebrae, which enables head rotation. These joints have a synovial cavity and are freely movable within their functional range.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Sebaceous glands are exocrine glands located within the dermis of the skin and are usually associated with hair follicles. They play an important role in maintaining skin and hair integrity by producing an oily secretion known as sebum. This secretion helps lubricate the skin, prevent water loss, and provide a protective antimicrobial barrier. Sebaceous gland activity is especially influenced by hormonal changes, particularly androgens.
A. Hormones: Sebaceous glands do not secrete hormones. Hormones are chemical messengers produced by endocrine glands such as the pituitary, thyroid, and adrenal glands. These substances are released directly into the bloodstream to regulate distant target organs. Sebaceous glands are exocrine in nature, meaning they secrete substances onto epithelial surfaces rather than into circulation.
B. Sweat containing water and electrolytes: This option describes the secretion of sweat glands, specifically eccrine sweat glands. These glands produce a watery fluid composed mainly of water, sodium chloride, and small amounts of metabolic waste to aid in thermoregulation. Sweat glands are structurally and functionally distinct from sebaceous glands. Sebaceous glands produce oily secretions, not watery sweat.
C. Keratinized epithelial cells: Keratinized epithelial cells are produced by keratinocytes in the epidermis, not by sebaceous glands. These cells form the outermost layer of the skin (stratum corneum) and provide a protective barrier against environmental damage and water loss. While sebaceous glands are associated with hair follicles in the skin, they do not produce keratinized cells.
D. Fat globules mixed with cellular debris: sebaceous glands secrete sebum, an oily substance composed primarily of lipids (fat globules), including triglycerides, wax esters, squalene, and cholesterol. This secretion also contains remnants of disintegrated gland cells due to holocrine secretion, where entire cells break down to release their contents. Sebum lubricates skin and hair, reduces water loss, and provides antimicrobial protection.
Correct Answer is B
Explanation
Biological organization in multicellular organisms follows a hierarchical structure that increases in complexity from the smallest functional components to complete organ systems. Each level builds upon the previous one, with specialized structures performing increasingly coordinated functions. This organization ensures efficiency in carrying out life processes such as metabolism, transport, and regulation. Understanding this hierarchy is fundamental to anatomy and physiology, as it explains how simple cellular components form complex living systems.
A. Cells → organelles → tissues → organs → organ systems: This option reverses the relationship between cells and organelles. Organelles are subcellular structures found within cells and therefore must come before cells in the hierarchy. Placing cells before organelles disrupts the correct progression of biological organization. While the rest of the sequence is partially correct, the initial order makes the entire option inaccurate.
B. Organelles → cells → tissues → organs → organ systems: This accurately reflects the increasing levels of biological organization. Organelles are the smallest functional structures within cells, performing specific tasks such as energy production or protein synthesis. Cells are the basic units of life, which combine to form tissues with specialized functions. Tissues then form organs, and organs work together in organ systems to maintain the survival of the organism.
C. Tissues → organelles → cells → organs → organ systems: This option places tissues before cells and organelles, which reverses the correct biological hierarchy. Tissues are composed of groups of cells, not the other way around. Additionally, organelles must exist within cells, so they cannot follow tissues in the sequence. This disrupts the foundational structure of biological organization.
D. Organ systems → organs → tissues → cells → organelles: This presents a decreasing order of complexity rather than an increasing one. While organ systems are the highest level of organization, they should appear last in a sequence showing increasing complexity. This arrangement reverses the correct physiological progression from simple to complex structures.
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