HESI A2 Elsevier (HESI): HESI Admission Assessment - Set 4 - Part 1

Correct Answer: Anterior

Anterior, also known as ventral, refers to body parts located toward the front of the body. In standard anatomical position the sternum is anterior to the spine, and the toes are anterior to the heel. Option a is incorrect because Posterior, also called dorsal, refers to structures located toward the back of the body, the opposite of anterior. The spine is posterior to the sternum and heart, not in front. Option b is incorrect because Lateral describes a position farther from the midline of the body, while medial means closer. It is used along the side-to-side axis and does not indicate front-to-back orientation of structures. Option d is incorrect because Superior means toward the head or upper portion of the body, while inferior means toward the feet. Superior refers to vertical position rather than front-to-back orientation along the anterior-posterior axis.

Correct Answer: Midsagittal plane

The midsagittal plane is a vertical plane passing directly through the midline of the body. It divides the body into equal right and left halves and runs front to back. Option b is incorrect because The frontal, or coronal, plane is a vertical plane that divides the body into anterior and posterior portions. It does not produce equal right and left halves of the body. Option c is incorrect because The transverse, or horizontal, plane runs perpendicular to the long axis of the body. It divides the body into superior and inferior portions and does not separate right and left halves. Option d is incorrect because An oblique plane cuts the body at an angle other than ninety degrees to the standard planes. It produces unequal sections and is not used to define right and left halves.

Correct Answer: Thoracic cavity

The thoracic cavity is enclosed by the ribcage and the diaphragm. It contains the heart within the mediastinum, the lungs within their pleural cavities, and major vessels including the aorta and venae cavae. Option a is incorrect because The abdominal cavity contains the stomach, liver, pancreas, spleen, and most of the intestines. It lies inferior to the diaphragm and does not house the heart, lungs, or major thoracic vessels. Option b is incorrect because The cranial cavity is part of the dorsal body cavity and contains the brain. It is formed by the bones of the skull and does not house the heart or lungs. Option c is incorrect because The pelvic cavity contains the urinary bladder, parts of the reproductive system, and the rectum. It lies far inferior to the diaphragm and does not contain the heart or lungs.

Correct Answer: Maintaining a stable internal environment

Homeostasis is the maintenance of a relatively stable internal environment despite changes occurring outside the body. Variables like body temperature, blood glucose, and pH are tightly regulated within narrow physiologic ranges. Option a is incorrect because Breaking down glucose for energy describes cellular respiration, which occurs in the mitochondria of cells. Although respiration supports homeostasis, it is one process and not the overall definition of internal regulation. Option c is incorrect because Defending the body against infection describes immunity, a function of the immune system and white blood cells. Immunity supports survival and contributes to homeostasis but is not the definition of internal stability itself. Option d is incorrect because Passing genetic material to offspring describes reproduction, which is needed to continue the species. Reproduction is a characteristic of living things but is not the definition of internal stability called homeostasis.

Correct Answer: Proximal

Proximal means closer to the point of attachment of a limb to the trunk. For example, the shoulder is proximal to the elbow, and the elbow is proximal to the wrist. Option a is incorrect because Distal means farther from the point of attachment of a limb to the trunk. The fingers are distal to the elbow because they are farther from where the arm attaches. Option b is incorrect because Superficial means closer to the surface of the body and is the opposite of deep. It is used along the surface-to-interior axis of the body, not the proximal-distal axis used for the limbs. Option d is incorrect because Medial means closer to the midline of the body, while lateral means farther from the midline. These terms describe side-to-side position rather than position along the length of an attached limb.

Correct Answer: Mitochondrion

The mitochondrion is the primary site of ATP production. It performs the citric acid cycle and oxidative phosphorylation, generating most of the energy used by the cell during aerobic respiration. Option b is incorrect because Ribosomes synthesize proteins by translating messenger RNA into chains of amino acids. They consume ATP during translation rather than producing it and are not the main source of cellular energy. Option c is incorrect because Lysosomes are membrane-bound organelles that contain digestive enzymes. They break down worn organelles, food particles, and engulfed pathogens, supporting waste removal and recycling but not generating ATP for the cell. Option d is incorrect because The Golgi apparatus modifies, sorts, and packages proteins and lipids into vesicles for secretion or delivery within the cell. It does not produce ATP through cellular respiration or other pathways.

Correct Answer: Epithelial tissue

Epithelial tissue covers body surfaces, lines internal cavities and vessels, and forms glands. The epidermis of the skin is epithelial, and a simple squamous epithelium called endothelium lines blood vessels. Option a is incorrect because Muscle tissue contracts to produce movement and includes skeletal, smooth, and cardiac varieties. It moves the body, propels substances through hollow organs, and pumps blood, but does not form linings. Option b is incorrect because Connective tissue supports, binds, and protects other tissues throughout the body. Examples include bone, cartilage, blood, and adipose tissue, but connective tissue does not form the surface linings of vessels and skin. Option c is incorrect because Nervous tissue conducts electrical impulses and includes neurons and supporting neuroglial cells. It is found within the brain, spinal cord, and peripheral nerves, not forming a covering or surface layer of organs.

Correct Answer: Cell

The cell is the basic structural and functional unit of all living organisms. Every organism is composed of one or more cells, and according to cell theory all cells arise from preexisting cells. Option a is incorrect because A tissue is a group of similar cells working together to perform a specific function. Tissues are formed from cells but are not themselves the basic unit of life that makes up organisms. Option c is incorrect because An organ is a structure made of two or more tissues that work together to perform a specific function. Organs such as the heart and stomach are organized at a higher level than the cell. Option d is incorrect because A molecule is a chemical structure made of two or more atoms held together by bonds. Molecules are smaller than cells and are not themselves alive, so they cannot be the basic unit of life.

Correct Answer: Meiosis

Meiosis produces four haploid gametes from one diploid parent cell. The chromosome number is reduced by half so that fertilization can restore the normal diploid number in the resulting offspring. Option a is incorrect because Mitosis produces two genetically identical diploid daughter cells from one parent cell. It is responsible for growth, tissue repair, and replacement of worn cells, but it does not form gametes. Option b is incorrect because Binary fission is a form of asexual reproduction used by bacteria and some other prokaryotes. It does not occur in human cells and does not produce gametes with reduced chromosome numbers. Option d is incorrect because Cytokinesis is the division of the cytoplasm that follows nuclear division during cell division. It is a step within both mitosis and meiosis rather than a separate type of cell division.

Correct Answer: Active transport

Active transport moves substances against their concentration gradient and requires energy from ATP. The sodium-potassium pump is the classic example, actively moving sodium ions out of cells and potassium ions into cells. Option b is incorrect because Simple diffusion is the passive movement of small nonpolar molecules from an area of high concentration to one of low concentration. It does not require ATP energy or transport proteins. Option c is incorrect because Osmosis is the passive movement of water across a selectively permeable membrane from low to high solute concentration. It moves down a water concentration gradient and does not require ATP energy. Option d is incorrect because Facilitated diffusion uses transport proteins to move molecules down their concentration gradient. It is a passive process and does not consume ATP for the actual transport step across the membrane.

Correct Answer: Epidermis

The epidermis is the outermost layer of the skin and is composed of stratified squamous epithelium. Its keratinocytes produce keratin, a tough protein that forms a protective barrier against the environment. Option a is incorrect because The hypodermis lies beneath the dermis and consists of loose connective tissue and adipose tissue. It anchors the skin to underlying structures and is the deepest layer, not the outer surface. Option b is incorrect because The dermis lies beneath the epidermis and contains blood vessels, nerves, hair follicles, and glands. Although it is thick and important, it is covered by the epidermis and is not the outermost layer. Option c is incorrect because The subcutaneous layer is another name for the hypodermis. It lies below the dermis, contains fat for insulation and cushioning, and is the deepest of the three layers of the skin.

Correct Answer: Keratin

Keratin is a tough fibrous protein produced by keratinocytes in the epidermis. As cells move toward the surface they fill with keratin, creating a durable, waterproof barrier against abrasion and water loss. Option a is incorrect because Collagen is a structural protein that provides tensile strength to the dermis, bones, tendons, and other connective tissues. It is not the protein responsible for waterproofing or toughening the epidermis. Option c is incorrect because Elastin gives connective tissues their stretch and recoil properties. It is found in the dermis and in elastic arteries and lung tissue, but it does not waterproof or toughen the epidermis. Option d is incorrect because Melanin is a pigment produced by melanocytes in the epidermis. It determines skin color and absorbs harmful ultraviolet radiation, but it does not provide toughness or waterproofing to the skin surface.

Correct Answer: Production of digestive enzymes

Production of digestive enzymes is a function of the digestive system, performed by glands such as the salivary glands, stomach, and pancreas. The skin is not involved in producing digestive enzymes for food breakdown. Option b is incorrect because Protection against pathogens is a major function of the integumentary system. The intact epidermis acts as a physical barrier preventing most microbes from entering the body, supported by sebum and antimicrobial peptides. Option c is incorrect because Regulation of body temperature is a key role of the integumentary system. Sweating provides evaporative cooling, while changes in blood flow through the dermis help dissipate excess heat or conserve body warmth. Option d is incorrect because Synthesis of vitamin D occurs in the skin when ultraviolet light converts a cholesterol derivative into a precursor of active vitamin D. This is a recognized and important function of the integumentary system.

Correct Answer: Full-thickness burn

A full-thickness burn destroys the entire epidermis and dermis and may damage muscle or bone. The area often appears white, leathery, or charred and is often painless centrally because nerve endings are destroyed. Option a is incorrect because A superficial burn affects only the epidermis. The skin appears red and is painful but does not blister or destroy the dermis. A typical mild sunburn is an example of this kind of injury. Option b is incorrect because A partial-thickness burn damages the epidermis and part of the dermis. It is painful and typically blistered, but the deeper structures and the full thickness of the dermis are not destroyed by this burn. Option d is incorrect because A first-degree burn is another name for a superficial burn that affects only the epidermis. It is the least severe type of burn and does not extend through the dermis to underlying tissues.

Correct Answer: Sudoriferous gland

Sudoriferous, or sweat, glands secrete sweat onto the skin surface. As the watery sweat evaporates it carries heat away from the body, which is the primary mechanism of evaporative cooling in humans. Option a is incorrect because Sebaceous glands secrete sebum, an oily mixture that lubricates the skin and hair and provides some antimicrobial protection. Sebum coats the surface but does not evaporate to cool the body during heat stress. Option b is incorrect because Hair follicles produce hair shafts that provide minor insulation and protection. They do not produce a watery secretion that evaporates to cool the body and are not the main thermoregulatory structure of the skin. Option c is incorrect because The arrector pili muscle contracts to make a hair stand upright, producing goose bumps. This response traps a thin layer of air for insulation against cold rather than dissipating heat by evaporative cooling.

Correct Answer: Production of antibodies

Production of antibodies is performed by plasma cells of the immune system, which are derived from B lymphocytes. Bones house the marrow that produces immune cells, but they do not directly secrete antibodies. Option a is incorrect because Support of the body is a primary function of the skeletal system. The bones form the rigid framework that holds the body upright, supports soft tissues, and provides attachment points for skeletal muscles. Option c is incorrect because Storage of calcium is a major function of bone tissue. The skeleton holds a large reservoir of calcium ions that are released into or deposited from the blood to maintain stable plasma calcium levels. Option d is incorrect because Production of blood cells, called hematopoiesis, occurs in the red bone marrow within certain bones. Red marrow forms red blood cells, white blood cells, and platelets, making blood production a recognized skeletal function.

Correct Answer: Long bones

Long bones are longer than they are wide, with a shaft called the diaphysis and two ends called epiphyses. The femur of the thigh and the humerus of the upper arm are classic long bones. Option a is incorrect because Short bones are roughly cube-shaped, with width similar to length, such as the carpals of the wrist and tarsals of the ankle. The femur and humerus are far longer than they are wide. Option b is incorrect because Flat bones are thin, broad, and often curved, including the sternum, ribs, scapulae, and many cranial bones. They protect organs and provide muscle attachment but are not classified the same as the femur. Option d is incorrect because Irregular bones have complex shapes that do not fit into other categories, such as vertebrae, the sacrum, and many facial bones. Long bones with elongated shafts like the femur are not in this group.

Correct Answer: Fibrous joint

Fibrous joints connect bones with dense connective tissue and allow little or no movement. The sutures of the skull are immovable fibrous joints that fuse the cranial bones into a protective vault around the brain. Option b is incorrect because Cartilaginous joints, such as the pubic symphysis and intervertebral discs, are connected by cartilage and allow only slight movement. The sutures of the skull are bound by fibrous tissue, not cartilage. Option c is incorrect because Synovial joints, such as the shoulder, knee, and elbow, contain a fluid-filled cavity and allow free movement. The bones of the skull are tightly bound and are not freely movable like synovial joints. Option d is incorrect because A ball-and-socket joint is a type of synovial joint found at the hip and shoulder, allowing movement in many directions. Skull bones do not articulate in this way and are not freely movable structures.

Correct Answer: Parathyroid hormone

Parathyroid hormone, secreted by the parathyroid glands, raises blood calcium levels. It stimulates osteoclasts to release calcium from bone, increases calcium reabsorption in the kidneys, and promotes activation of vitamin D. Option a is incorrect because Calcitonin, secreted by the thyroid gland, lowers blood calcium by inhibiting osteoclasts and promoting calcium deposition in bone. Its action opposes that of parathyroid hormone and is most important during periods of high calcium. Option b is incorrect because Insulin is secreted by beta cells of the pancreas and lowers blood glucose by promoting cellular uptake of sugar. It regulates carbohydrate metabolism and does not directly raise or lower blood calcium levels. Option c is incorrect because Cortisol is a glucocorticoid produced by the adrenal cortex that affects glucose metabolism, immune function, and the stress response. It can weaken bone over time but does not primarily regulate blood calcium.

Correct Answer: Spongy bone of the epiphysis

Spongy bone in the epiphyses of long bones contains red marrow in adults. Red marrow carries out hematopoiesis, producing red blood cells, white blood cells, and platelets that enter the circulation through nearby vessels. Option a is incorrect because The diaphysis is the shaft of a long bone. In adults its central medullary cavity is filled mostly with yellow marrow, which stores fat for energy reserve rather than producing blood cells. Option b is incorrect because The periosteum is the dense fibrous membrane covering the outer surface of bone. It contains blood vessels, nerves, and bone-forming cells but does not house red marrow or carry out hematopoiesis. Option d is incorrect because The medullary cavity is the hollow center of the diaphysis of a long bone. In adults it contains primarily yellow marrow with very limited hematopoietic activity compared with the spongy bone of the epiphysis.