Bio 161: Anatomy and Physiology Final Exam

Correct Answer:

C. Regeneration

Explanation

Regeneration is a hallmark property of epithelial tissue. Epithelial cells have a short life span, typically 2–6 days, and are continuously replaced by stem cells located in the basal layer. This rapid turnover allows epithelial tissue to repair itself quickly after injury, such as cuts, abrasions, or burns. The regenerative ability is essential for maintaining protective barriers and ensuring proper tissue function even after damage.

Why Other Options Are Wrong

A. Vascularity

Epithelial tissue is avascular, meaning it has no direct blood supply. Nutrients and oxygen diffuse from the underlying connective tissue. Vascularity does not explain the process of wound healing through stem cell replacement.

B. Sensation

Sensation refers to the presence of sensory nerve endings in epithelial tissue that detect stimuli such as touch, temperature, and pain. While important, it does not account for the replacement of cells after injury.

D. Protection

Protection describes the barrier function of epithelial tissue, which prevents damage from pathogens, chemicals, and physical forces. While protection is enhanced by regeneration, the specific property described is the replacement of damaged cells by stem cells.

Correct Answer:

C. Hydrophilic

Explanation

Hydrophilic literally means “water-loving” and refers to molecules or regions of molecules that readily interact with water. In the plasma membrane, the phosphate heads of phospholipids are hydrophilic and orient themselves toward the aqueous environments inside and outside of the cell. This property is critical for the bilayer structure, as it stabilizes the membrane and helps separate internal and external environments.

Why Other Options Are Wrong

A. Hydrophobic

Hydrophobic means “water-fearing” and refers to molecules that do not interact well with water. This term applies to the fatty acid tails of phospholipids, which turn inward away from water, not to the phosphate heads.

B. Amphipathic

Amphipathic describes molecules that have both hydrophilic and hydrophobic regions, such as an entire phospholipid. While correct for the whole phospholipid, the question asked specifically about the region that readily interacts with water, which is hydrophilic.

D. Lipophilic

Lipophilic means “fat-loving” and describes substances that dissolve easily in lipids or nonpolar environments. This property applies to the fatty acid tails of phospholipids, not to the phosphate heads, which interact with water.

Correct Answer:

D. All of the above

Explanation

Connective tissue contains multiple specialized cells with different but complementary functions. Macrophages and other white blood cells provide protection by engulfing pathogens and debris, serving as part of the immune system. Fibroblasts create collagen, elastin, and reticular fibers to form the extracellular matrix, giving tissues strength and flexibility. Adipocytes store lipids, insulate the body, and cushion organs. Together, these cells support, protect, and maintain the body’s tissues, demonstrating the multifunctional nature of connective tissue.

Why Other Options Are Wrong

A. Macrophages and other white blood cells (protection)

While correct about immune protection, this option ignores the roles of fibroblasts and adipocytes, which are also essential connective tissue cells.

B. Fibroblasts (produce fibers of the matrix)

Fibroblasts are key for producing protein fibers but do not handle immunity or fat storage. Focusing only on fibroblasts misses the broader variety of connective tissue cells.

C. Adipocytes (store lipids and cushion organs)

Adipocytes are vital for fat storage and insulation, but they do not produce fibers or fight infection. Limiting the answer to adipocytes alone would overlook other critical cell types.

Correct Answer:

B. Reticular layer → Papillary layer

Explanation

The dermis has two layers: the deeper reticular layer and the more superficial papillary layer. The reticular layer is made of dense irregular connective tissue and provides strength, resilience, and housing for glands and hair follicles. The papillary layer lies just beneath the epidermis and contains capillaries, sensory receptors, and dermal papillae that interlock with the epidermis. From inner to outer, the correct sequence is reticular followed by papillary.

Why Other Options Are Wrong

A. Papillary layer → Reticular layer

This order is reversed. The papillary layer is closer to the outside world, but the question specifically asked for the order from inner to outer. Therefore, papillary first is incorrect.

C. Epidermis → Reticular layer

The epidermis is not part of the dermis. While the reticular layer is part of the dermis, pairing it directly after the epidermis skips the papillary layer, making this option inaccurate.

D. Hypodermis → Papillary layer

The hypodermis lies below the dermis and is not considered part of the dermis. Listing hypodermis to papillary ignores the reticular layer and misidentifies the structural order within the dermis.

Correct Answer:

B. Elastic (conducting) arteries

Explanation

Elastic (conducting) arteries are the largest arteries in the body, including the aorta and pulmonary arteries. They contain abundant elastic fibers that allow them to expand during ventricular systole and recoil during diastole. This elasticity helps dampen fluctuations between systolic and diastolic pressures, ensuring a more continuous flow of blood. Their close proximity to the heart requires them to withstand high pressure and adapt to rapid changes in blood volume.

Why Other Options Are Wrong

A. Muscular (distributing) arteries

Muscular arteries distribute blood to specific organs and tissues. They contain more smooth muscle than elastic fibers and regulate blood flow by vasoconstriction or vasodilation, not by absorbing pressure changes.

C. Arterioles

Arterioles are small vessels that regulate resistance and control blood flow into capillary beds. They play a major role in blood pressure regulation but lack the high elasticity seen in conducting arteries.

D. Veins

Veins return blood to the heart under low pressure. They have thinner walls, larger lumens, and often contain valves, but they do not have the elastic properties necessary to absorb systolic-diastolic pressure changes.

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. 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 Answer:

C. Semi-permeable

Explanation

A semi-permeable membrane is one that allows some substances to pass through while preventing others from crossing. The plasma membrane demonstrates this property by permitting small nonpolar molecules, like oxygen and carbon dioxide, to diffuse freely, while restricting larger or charged molecules unless assisted by transport proteins. This selectivity is essential for maintaining homeostasis, regulating nutrient entry, and protecting the cell from harmful substances.

Why Other Options Are Wrong

A. Fully permeable

A fully permeable membrane would allow all substances, regardless of size or charge, to cross freely. This would disrupt homeostasis and expose the cell to harmful compounds. Since the plasma membrane is selective, not everything can pass.

B. Impermeable

An impermeable membrane would prevent any substances from crossing. This would cut the cell off from nutrients, oxygen, and waste removal. Because cells require constant material exchange to survive, the plasma membrane cannot be impermeable.

D. Non-permeable

Non-permeable is similar in meaning to impermeable, describing a barrier that does not allow any substances to cross. This does not fit the function of the plasma membrane, which must allow selective entry and exit of materials for the cell to function properly.

Correct Answer:

C. Number of layers of cells

Explanation

Epithelial tissue is classified based on two main features: the shape of the cells and the number of layers. When classified by the number of layers, there are two categories: simple epithelium, consisting of a single cell layer specialized for absorption, secretion, and filtration; and stratified epithelium, consisting of multiple layers designed for protection against abrasion and stress. This system helps distinguish epithelial types in various parts of the body.

Why Other Options Are Wrong

A. Shape of epithelial cells

Shape refers to classifications such as squamous (flat), cuboidal (cube-shaped), or columnar (tall), not the number of layers. The question specifically focused on layering, not shape.

B. Function of epithelial cells

Function includes absorption, secretion, filtration, or protection, but the classification discussed in the question is based on the number of layers, not what the cells do.

D. Location of epithelial cells

Location refers to where epithelium is found, such as in the lungs, intestines, or skin. While important, it is not the method of classification described here.