Bio 161: Anatomy and Physiology Final Exam

Correct Answers:

A. Digestive tract; B. Blood vessels; C. Respiratory passages; D. Surface of organs; E. Hollow, tubular organs

Explanation of Each Correct Answer

A. Digestive tract

Epithelial tissue lines the digestive tract, such as the stomach and intestines, where it controls absorption of nutrients and secretion of digestive fluids.

B. Blood vessels

The inner lining of blood vessels is composed of simple squamous epithelium, also called endothelium, which allows smooth blood flow and exchange of substances.

C. Respiratory passages

Epithelial tissue lines the respiratory tract, including the trachea and bronchi. It often has cilia and mucus-secreting cells to trap and remove particles.

D. Surface of organs

Epithelial tissue covers the outer surfaces of many organs, serving as a protective barrier and interface between the organ and its environment.

E. Hollow, tubular organs

Epithelial tissue lines hollow organs such as the bladder, intestines, and uterus, regulating absorption, secretion, and protection.

Why Other Options Are Wrong

F. Skeletal muscles

Skeletal muscles are composed of muscle tissue, not epithelial tissue. Their role is contraction and movement, not lining or covering surfaces.

Correct Answer:

B. Collagen

Explanation

Collagen is a fibrous protein that is long and string-like, forming strong fibers within connective tissue. It is the most abundant protein in the human body and provides tensile strength and structural support to tissues such as skin, tendons, ligaments, cartilage, and bone. Collagen fibers resist stretching, making them essential for maintaining tissue integrity under mechanical stress.

Why Other Options Are Wrong

A. Actin

Actin is a globular protein that forms microfilaments in the cytoskeleton and plays a role in cell shape, intracellular transport, and muscle contraction. It is not long, fibrous, or specialized for structural support in connective tissue like collagen.

C. Myosin

Myosin is a motor protein involved in muscle contraction, interacting with actin filaments to generate movement. While important for muscle physiology, it is not a fibrous protein that forms structural support fibers in connective tissues.

D. Keratin

Keratin is a fibrous protein found in epithelial cells, forming hair, nails, and the outer layer of skin. While strong and protective, keratin is specialized for epithelial structures, not for forming long connective tissue fibers like collagen.

Correct Answers:

A. Thermal regulation; B. Protection; C. Sensation; D. Vitamin D production; E. Excretion; F. Nonverbal communication

Explanation of Each Correct Answer

A. Thermal regulation

The integumentary system regulates body temperature through sweating, shivering, and adjusting blood vessel diameter. Vasodilation allows excess heat to escape, while vasoconstriction conserves heat. This function is essential for keeping the body’s internal environment stable and preventing overheating or hypothermia.

B. Protection

The skin acts as a barrier against pathogens, chemicals, UV radiation, and mechanical injury. The keratinized surface prevents water loss, sebum helps block harmful substances, and melanin protects against UV damage. Together, these protective mechanisms keep the body safe from external threats.

C. Sensation

Specialized sensory receptors in the skin detect touch, pressure, pain, and temperature. This allows the body to respond to environmental stimuli, avoid harm, and interact with surroundings. Without this function, individuals would be unable to detect injury or changes in temperature.

D. Vitamin D production

When exposed to ultraviolet (UV) light, the skin produces precursors of Vitamin D. These are later converted into calcitriol, which is essential for calcium absorption in the intestines. This process supports bone mineralization, growth, and overall skeletal health.

E. Excretion

Through sweat glands, the skin excretes small amounts of waste products such as salts, urea, and ammonia. Although the kidneys are the main excretory organs, the skin contributes by helping eliminate toxins and supporting homeostasis.

F. Nonverbal communication

The skin plays a role in nonverbal communication through facial expressions, blushing, and other visual cues. These expressions allow humans to communicate emotions like happiness, anger, or embarrassment without words, which is essential for social interaction.

Why Other Options Are Wrong

G. Digestion

Digestion is a function of the gastrointestinal system, not the integumentary system. The skin does not break down or absorb nutrients from food. While the skin can absorb some substances such as medications or toxins, this is not considered digestion.

Correct Answer:

B. Avascularity

Explanation

Avascularity is a defining property of epithelial tissue. Unlike connective tissue, epithelium does not contain blood vessels. Instead, it depends on the diffusion of nutrients and oxygen from capillaries located in the underlying connective tissue. This limitation explains why epithelial tissue is thin but also why it has a high regenerative capacity to maintain barrier function despite the lack of direct blood supply.

Why Other Options Are Wrong

A. Vascularity

Vascularity refers to the presence of blood vessels. Epithelial tissue is avascular, not vascular, so this choice contradicts the characteristic described.

C. Regeneration

Regeneration describes the ability of epithelial tissue to replace damaged or dead cells rapidly through stem cell activity. While related to healing, it does not explain how epithelial tissue receives nutrients without blood vessels.

D. Sensation

Sensation refers to the presence of sensory nerve endings in epithelial tissue, which allow detection of stimuli such as touch, temperature, and pain. This is unrelated to nutrient delivery or the absence of blood vessels.

Correct Answer:

A. Polarity

Explanation

Polarity is a structural property of epithelial tissue that refers to the presence of distinct surfaces. The apical surface faces outward toward the lumen or external environment and may have modifications such as cilia or microvilli. The basal surface anchors epithelial cells to the basement membrane, which connects them to underlying connective tissue. This polarity allows epithelial tissue to carry out directional processes such as absorption, secretion, and transport.

Why Other Options Are Wrong

B. Avascularity

Avascularity refers to the absence of blood vessels in epithelial tissue, requiring nutrients to diffuse from underlying connective tissue. While true for epithelium, it does not describe distinct surfaces like apical and basal.

C. Regeneration

Regeneration describes the ability of epithelial tissue to replace cells rapidly through stem cell division. While important for healing, it is unrelated to the structural polarity of epithelial cells.

D. Sensation

Sensation refers to the presence of nerve endings in epithelial tissue that allow detection of stimuli such as touch, temperature, and pain. This property does not explain the division into apical and basal surfaces.

Correct Answer:

C. Lymphoid hemopoiesis

Explanation

Lymphoid hemopoiesis occurs in lymphatic tissues and organs and is responsible for producing white blood cells, particularly lymphocytes. Unlike myeloid hemopoiesis in the red bone marrow, which produces all seven formed elements, lymphoid hemopoiesis is specialized for immune function. This process ensures the body maintains a supply of lymphocytes for defense against pathogens.

Why Other Options Are Wrong

A. Myeloid hemopoiesis

Myeloid hemopoiesis occurs in the red bone marrow and produces all formed elements, not just white blood cells. It is broader in scope than lymphoid hemopoiesis.

B. Erythropoiesis

Erythropoiesis is the production of red blood cells, stimulated by erythropoietin. It is part of myeloid hemopoiesis and does not occur in lymphatic organs.

D. Thrombopoiesis

Thrombopoiesis is the production of platelets from megakaryocytes in the bone marrow. It is unrelated to the production of white blood cells in lymphoid organs.

Correct Answer:

B. Elastic (conducting) arteries

Explanation

During systole, elastic (conducting) arteries such as the aorta expand as blood enters their lumen. Their abundance of elastic fibers allows them to absorb systolic pressure and store potential energy in their walls. This expansion reduces the workload on smaller arteries and helps maintain smooth blood flow. By stretching during systole and recoiling during diastole, these vessels prevent extreme fluctuations in blood pressure.

Why Other Options Are Wrong

A. Muscular (distributing) arteries

Muscular arteries regulate blood flow to specific organs through vasoconstriction and vasodilation. They lack the high concentration of elastic fibers needed to absorb systolic pressure surges.

C. Arterioles

Arterioles are small resistance vessels that control blood flow into capillaries. They do not expand significantly during systole and play little role in absorbing pressure fluctuations.

D. Veins

Veins carry blood back to the heart at low pressure. They do not experience systolic surges or expand in the same way as elastic arteries. Instead, they rely on valves and skeletal muscle pumps to aid venous return.

Correct Answer:

C. Stratum granulosum

Explanation

The stratum granulosum is composed of keratinocytes that begin producing keratin and lipids, which help create a water-resistant barrier for the skin. As keratinocytes reach this layer, they start to die, losing their nuclei and organelles. This layer provides protection against dehydration and external harm. It is also the second site where immune Langerhans cells can be found, reinforcing the skin’s defense role.

Why Other Options Are Wrong

A. Stratum basale

The stratum basale is the deepest layer of the epidermis and contains mitotically active keratinocytes, melanocytes, and Merkel cells. It is not where keratin and lipids accumulate or where keratinocytes die. Its function is cell regeneration, not water barrier formation.

B. Stratum spinosum

The stratum spinosum is made of living keratinocytes connected by desmosomes, giving it a spiny appearance. While it does contain Langerhans cells, keratin and lipid accumulation does not occur here, and the keratinocytes are not yet dead.

D. Stratum corneum

The stratum corneum is the outermost epidermal layer made of fully dead keratinocytes stacked in multiple layers. While it provides a barrier, this is the result of earlier processes in the stratum granulosum. The corneum does not produce keratin or lipids; it simply contains the end product.

Correct Answer:

B. Hemopoietic stem cells (HSC)

Explanation

Hemopoietic stem cells (HSC) are pluripotent stem cells located in the red bone marrow that generate all of the formed elements of blood. These include red blood cells, white blood cells, and platelets. HSCs continually divide and differentiate to replace aging or damaged blood cells, ensuring proper oxygen transport, immunity, and clotting. Their critical role is the foundation of hematopoiesis, making them essential for survival.

Why Other Options Are Wrong

A. Totipotent stem cells

Totipotent stem cells exist only in early embryonic development and can generate all tissues, including extraembryonic structures like the placenta. They are not present in bone marrow and do not specifically generate blood cells.

C. Multipotent mesenchymal stem cells

Mesenchymal stem cells in bone marrow give rise to bone, cartilage, and fat cells, not to all formed elements of the blood. They support skeletal and connective tissue development rather than hematopoiesis.

D. Unipotent stem cells

Unipotent stem cells produce only one specialized cell type, such as skin stem cells generating keratinocytes. They lack the ability to generate the multiple formed elements of blood.