Bio 201 Human Anatomy and Physiology

Correct Answer:

atom

Explanation:

The atom is the smallest unit of matter that retains the properties of an element. Atoms consist of protons, neutrons, and electrons, and they combine to form molecules, which then make up the structures of living and nonliving things. In biology, atoms such as carbon, hydrogen, oxygen, and nitrogen are especially important because they form the building blocks of biomolecules essential for life. Without atoms, larger structures like cells, tissues, and organs could not exist.

Why Other Options Are Wrong:

cell

This is incorrect because the cell is the basic unit of life, not matter. Cells are composed of atoms and molecules, making them structurally more complex.

tissue

This is incorrect because tissues are groups of similar cells working together to perform a specific function. They are at a higher level of organization than atoms and cells.

organ

This is incorrect because organs are composed of multiple tissues working together. They represent an even higher level of organization beyond tissues, cells, and atoms.

system

This is incorrect because a system is the highest level listed here, consisting of multiple organs working together. It is far above the atomic level and does not qualify as the basic unit of matter.

Correct Answer:

centriole

Explanation:

Centrioles are cylindrical organelles made of microtubules, usually found in pairs arranged at right angles to each other. They play a critical role during cell division by organizing the mitotic spindle, which helps move and separate chromosomes into daughter cells. Their perpendicular arrangement ensures proper anchoring and orientation of spindle fibers.

Why Other Options Are Wrong:

Golgi apparatus

This is incorrect because the Golgi apparatus modifies, packages, and ships proteins and lipids. It does not organize spindle fibers or move chromosomes.

mitochondrion

This is incorrect because mitochondria are the "powerhouses" of the cell, generating ATP through aerobic respiration. They do not function in chromosome movement.

endoplasmic reticulum

This is incorrect because the endoplasmic reticulum (smooth and rough ER) synthesizes lipids, proteins, and transports materials. It is not involved in spindle formation or chromosome movement.

ribosome

This is incorrect because ribosomes are the sites of protein synthesis. They do not assist in moving chromosomes during cell division.

Correct Answer:

cuticle-cortex-medulla

Explanation:

The hair shaft has three distinct layers arranged from the outside to the inside. The outermost layer is the cuticle, a protective layer of overlapping, scale-like cells that prevents damage. Beneath it lies the cortex, which makes up the bulk of the hair and contains keratin and pigment (melanin) that gives hair its color. The innermost layer is the medulla, which may be absent in very fine hair and consists of loosely packed cells and air spaces.

Why Other Options Are Wrong:

cortex-cuticle-medulla

This is incorrect because the cortex is not the outermost layer; the cuticle always surrounds the cortex.

medulla-cortex-cuticle

This is incorrect because it reverses the order. The medulla is at the core, the cortex surrounds it, and the cuticle forms the outer protective layer.

Correct Answer:

nucleus

Explanation:

The nucleus is an organelle found in eukaryotic cells. It serves as the control center of the cell, housing DNA and coordinating activities such as growth, metabolism, protein synthesis, and cell division. Organelles are specialized structures within cells that perform distinct functions necessary for survival. The nucleus is one of the most important organelles because it contains genetic instructions essential for life and cellular regulation.

Why Other Options Are Wrong:

oxygen

This is incorrect because oxygen is a molecule necessary for respiration and energy production, but it is not a cellular structure.

glucose

This is incorrect because glucose is a simple sugar molecule used by cells to produce energy. It is a nutrient, not an organelle.

water

This is incorrect because water is a molecule that serves as a solvent and medium for biochemical reactions. It does not function as a specialized cell structure.

tissue

This is incorrect because tissue is a group of similar cells working together to perform a function. It is a higher level of organization than organelles, which exist inside individual cells.

Correct Answer:

tight junctions

Explanation:

Tight junctions are special connections between adjacent cells where membrane proteins interlock to form a seal. This prevents substances from leaking between cells and forces materials to pass through the cells instead. They are especially important in epithelial tissues, such as the lining of the intestines and the blood-brain barrier, where selective permeability is crucial.

Why Other Options Are Wrong:

gap junctions

This is incorrect because gap junctions are protein channels that allow communication and passage of ions and small molecules between cells, not barriers.

desmosomes

This is incorrect because desmosomes are anchoring junctions that hold cells together, providing strength against mechanical stress. They do not prevent material from passing between cells.

centrioles

This is incorrect because centrioles are organelles that organize spindle fibers during cell division. They are not cell junctions.

microvilli

This is incorrect because microvilli are fingerlike projections of the plasma membrane that increase surface area for absorption. They are not intercellular junctions.

Correct Answer:

epidermis, dermis, hypodermis

Explanation:

The correct order of skin layers from the surface inward is epidermis → dermis → hypodermis. The epidermis is the thin, outer layer made of stratified squamous epithelium that provides protection. Beneath it lies the dermis, a thicker connective tissue layer containing blood vessels, nerves, and glands. The deepest layer is the hypodermis (subcutaneous layer), composed mainly of adipose and areolar tissue, which insulates, cushions, and anchors the skin to underlying structures.

Why Other Options Are Wrong:

dermis, epidermis, hypodermis

This is incorrect because the dermis is deeper than the epidermis, not superficial to it.

hypodermis, epidermis, dermis

This is incorrect because the hypodermis is the deepest layer, not the most superficial.

epidermis, hypodermis, dermis

This is incorrect because the hypodermis lies beneath the dermis, not between the epidermis and dermis.

Correct Answer:

endoplasmic reticulum

Explanation:

The endoplasmic reticulum (ER) is a system of interconnected membrane-bound channels called cisternae. The rough ER, studded with ribosomes, is involved in protein synthesis and modification, while the smooth ER is responsible for lipid synthesis, detoxification, and calcium storage. Its cisternae provide a large surface area for biochemical reactions and transport of materials within the cell.

Why Other Options Are Wrong:

Golgi apparatus

This is incorrect because the Golgi apparatus also contains cisternae but is organized into stacked, flattened sacs specifically for modifying, sorting, and packaging proteins and lipids. It is not the widespread channel system found throughout the cytoplasm like the ER.

lysosomes

This is incorrect because lysosomes are membrane-bound vesicles containing digestive enzymes to break down cellular waste. They are not a system of cisternae.

ribosomes

This is incorrect because ribosomes are small, non-membranous structures that synthesize proteins. They are not channel systems and lack cisternae.

mitochondria

This is incorrect because mitochondria are double-membraned organelles that produce ATP through cellular respiration. They contain cristae, not cisternae.

Correct Answer:

blast

Explanation:

In connective tissue terminology, the suffix -blast refers to an immature, active cell that secretes the extracellular matrix. Examples include fibroblasts (which secrete fibers in connective tissue proper), chondroblasts (which produce cartilage matrix), and osteoblasts (which form bone matrix). These cells are metabolically active and essential for tissue growth and repair. Over time, they typically mature into less active -cytes, which maintain the matrix rather than secrete it.

Why Other Options Are Wrong:

chondro

This is incorrect because chondro- is a prefix that means cartilage. It does not by itself mean “immature” or “matrix-secreting.”

cyte

This is incorrect because -cyte refers to a mature cell that maintains tissue rather than secretes matrix. For example, chondrocytes maintain cartilage but do not actively secrete large amounts of new matrix.

fibro

This is incorrect because fibro- is a prefix meaning fiber. It is part of terms like fibroblast (a fiber-forming cell) but does not by itself mean “immature” or “matrix-secreting.”

Correct Answer:

cranial

Explanation:

The cranial cavity is the specific body cavity that houses and protects the brain. It is part of the dorsal cavity and is enclosed by the skull bones, which provide structural protection. The cranial cavity also contains meninges and cerebrospinal fluid, which cushion the brain and help maintain a stable environment. This cavity is vital because it safeguards one of the most important organs in the body while allowing space for blood vessels and nerves to pass.

Why Other Options Are Wrong:

thoracic

This is incorrect because the thoracic cavity lies in the chest region and contains the lungs, heart, esophagus, and trachea. It does not enclose the brain.

ventral

This is incorrect because the ventral cavity is a broad term that includes both the thoracic and abdominopelvic cavities. It does not specifically house the brain, as it is located in the anterior body regions.

abdominopelvic

This is incorrect because the abdominopelvic cavity is located below the diaphragm and contains organs such as the stomach, intestines, liver, bladder, and reproductive organs. It has no connection to the brain.

vertebral

This is incorrect because the vertebral cavity contains and protects the spinal cord. Although it is part of the dorsal cavity like the cranial cavity, it does not contain the brain