BCS 165 Unit 1 Exam Study Guide PDF

**Lexus Newlyn** **BCS 165 Unit 1 Exam Study Guide** **Chapter 1: The Sciences of Anatomy and Physiology** **Describe the Different Levels of Levels of Organization in the Human Body:** 1. **Chemical Level**: Includes atoms and molecules (e.g., water, glucose). 2. **Cellular Level**: Basi...

**Lexus Newlyn** **BCS 165 Unit 1 Exam Study Guide** **Chapter 1: The Sciences of Anatomy and Physiology** **Describe the Different Levels of Levels of Organization in the Human Body:** 1. **Chemical Level**: Includes atoms and molecules (e.g., water, glucose). 2. **Cellular Level**: Basic unit of life (e.g., muscle cells, nerve cells). 3. **Tissue Level**: Groups of similar cells performing a common function (e.g., epithelial, connective tissues). 4. **Organ Level**: Structures composed of two or more tissue types (e.g., heart, lungs). 5. **Organ System Level**: Groups of organs working together (e.g., digestive system). 6. **Organism Level**: The entire living being (e.g., a human). **Describe Anatomical Positions:** - **Anterior (Ventral)**: Toward the front (e.g., chest). - **Posterior (Dorsal)**: Toward the back (e.g., spine). - **Contralateral**: Opposite sides (e.g., right arm and left leg). - **Ipsilateral**: Same side (e.g., right arm and right leg). - **Deep**: Away from the surface (e.g., bones). - **Superficial**: Near the surface (e.g., skin). - **Distal**: Farther from the attachment point (e.g., fingers are distal to the shoulder). - **Proximal**: Closer to the attachment point (e.g., shoulder is proximal to the fingers). - **Inferior (Caudal)**: Below (e.g., stomach is inferior to the heart). - **Superior (Cranial)**: Above (e.g., head is superior to the chest). - **Lateral**: Away from the midline (e.g., ears are lateral to the nose). - **Medial**: Toward the midline (e.g., nose is medial to the eyes). **Describe Anatomical Regions of the Body:** - **Abdominal**: Abdomen area. - **Acromial**: Shoulder. - **Antebrachial**: Forearm. - **Antecubital**: Front of the elbow. - **Mental**: Chin. - **Nasal**: Nose. - **Occipital**: Back of the head. - **Olecranal**: Back of the elbow. - **Axillary**: Armpit. - **Brachial**: Upper arm. - **Buccal**: Cheek. - **Calcaneal**: Heel. - **Carpal**: Wrist. - **Cephalic**: Head. - **Cervical**: Neck. - **Coxal**: Hip. - **Cranial**: Skull. - **Crural**: Shin. - **Digits/Phalanges**: Fingers and toes. - **Dorsum**: Back. - **Facial**: Face. - **Femoral**: Thigh. - **Gluteal**: Buttocks. - **Inguinal**: Groin. - **Lower Extremity**: Hip to toes. - **Lumbar**: Lower back. - **Mammary**: Breast. - **Manus**: Hand. - **Oral**: Mouth. - **Orbital**: Eye socket. - **Otic**: Ear. - **Palmar**: Palm. - **Patellar**: Front of the knee. - **Pedal**: Foot. - **Pelvic**: Pelvis region. - **Plantar**: Sole of the foot. - **Popliteal**: Back of the knee. - **Pubic**: Genital area. - **Sacral**: Base of the spine. - **Scapular**: Shoulder blade. - **Sternal**: Breastbone. - **Sural**: Calf. - **Tarsal**: Ankle. - **Thoracic**: Chest. - **Trunk**: Body excluding limbs. - **Umbilical**: Navel. - **Upper Extremity**: Shoulder to fingers. - **Vertebral**: Spinal column. **Describe Body Cavities:** - **Cranial Cavity**: Contains the brain. - **Spinal (Vertebral) Cavity**: Contains the spinal cord. - **Thoracic Cavity**: Contains heart and lungs. - **Abdominal Cavity**: Contains digestive organs. - **Pelvic Cavity**: Contains reproductive organs, bladder. - **Abdominopelvic Cavity**: Combination of abdominal and pelvic cavities. - **Dorsal Cavity**: Includes cranial and spinal cavities. - **Ventral Cavity**: Includes thoracic and abdominopelvic cavities. - **Diaphragm**: Muscle separating thoracic and abdominal cavities. - **Mediastinum**: Central part of the thoracic cavity. - **Pericardial Cavity**: Surrounds the heart. - **Pleural Cavities**: Surround the lungs. **Abdominal Quadrants:** - **Right Upper Quadrant (RUQ)** - **Left Upper Quadrant (LUQ)** - **Right Lower Quadrant (RLQ)** - **Left Lower Quadrant (LLQ)** **Know the Difference Parietal vs. Visceral Serous Membrane:** - **Parietal**: Lines cavity walls. - **Visceral**: Covers organs. **Know the Homeostatic Control System Steps:** 1. **Stimulus**: Change detected in the environment. 2. **Receptor**: Detects the stimulus. 3. **Control Center**: Processes information and decides response. 4. **Effector**: Carries out the response to restore balance. **Chapter 2: Atoms, Ions, and Molecules & Chapter 3: Energy, Chemical Reactions, and Cellular Respiration** **Describe the Difference Dehydration Synthesis vs. Hydrolysis** - **Dehydration Synthesis:** A chemical reaction where two molecules are joined together by removing a water molecule. This process is used to build larger macromolecules like proteins, carbohydrates, and nucleic acids. - **Hydrolysis:** The opposite of dehydration synthesis. It breaks down larger molecules into smaller units by adding water. This is common during digestion when macromolecules are broken into monomers. **Describe Anabolic vs. Catabolic Reactions** - **Anabolic Reactions:** Build larger molecules from smaller ones, requiring energy (endothermic). Example: synthesis of proteins from amino acids. - **Catabolic Reactions:** Break down larger molecules into smaller ones, releasing energy (exothermic). Example: cellular respiration breaking down glucose. **Know the Definitions for These Mixtures and Measurements** - **Solutes:** The substances dissolved in a solution (e.g., salt in saltwater). - **Solution:** A homogeneous mixture where the solute is completely dissolved in the solvent (e.g., sugar in water). - **Colloid:** A mixture where particles are dispersed but not dissolved, and they do not settle out (e.g., milk, gelatin). - **Suspension:** A heterogeneous mixture with large particles that settle out over time (e.g., sand in water, blood). - **Mass:** The amount of matter in an object, measured in grams (g), kilograms (kg), etc. - **Volume:** The amount of space an object or substance occupies, measured in liters (L), milliliters (mL), etc. - **Molarity (M):** A measure of concentration, defined as moles of solute per liter of solution (mol/L). - **Molality (m):** A measure of concentration, defined as moles of solute per kilogram of solvent (mol/kg). - **Osmoles:** A measure of solute particles in a solution that contribute to osmotic pressure. - **Osmolarity:** The number of osmoles of solute per liter of solution (Osm/L). - **Osmolality:** The number of osmoles of solute per kilogram of solvent (Osm/kg). **Describe the Following Biological Macromolecules and Provide Examples of Each Kind** 1. **Lipids:** Non-polar molecules used for long-term energy storage, insulation, and cell membrane structure. - Examples: **Triglycerides** (fats/oils), **Phospholipids** (cell membranes), **Steroids** (cholesterol, hormones), **Eicosanoids** (prostaglandins for inflammation). 2. **Carbohydrates:** Provide quick energy and structural support. - Examples: **Monosaccharides** (glucose, fructose), **Disaccharides** (sucrose, lactose), **Polysaccharides** (starch, glycogen, cellulose). 3. **Nucleic Acids:** Store and transmit genetic information. - Examples: **DNA** (stores genetic code), **RNA** (protein synthesis), **ATP** (cellular energy). 4. **Proteins:** Perform structural, enzymatic, and regulatory functions. - Examples: **Enzymes** (catalase), **Hormones** (insulin), **Antibodies** (immune defense), **Structural Proteins** (collagen, keratin). **What is Protein Denaturation?** - **Definition:** The process where a protein loses its three-dimensional structure due to external stress like heat, pH changes, or chemicals. This loss of structure causes the protein to lose its function. - **Example:** Cooking an egg causes the egg white proteins to denature, turning from clear to white. **Chapter 4: Biology of the Cell** **Describe the Cellular Structures and Organelles** 1. **Centrioles**: Cylinder-shaped structures made of microtubules. They play a key role in cell division by helping organize the mitotic spindle. 2. **Cytoplasm and Cytosol**: - **Cytoplasm**: The entire contents within the cell membrane, excluding the nucleus. It includes cytosol, organelles, and inclusions. - **Cytosol**: The fluid portion of the cytoplasm where metabolic reactions occur. 3. **Cytoskeleton**: A network of protein filaments (microfilaments, intermediate filaments, and microtubules) that provide structural support, aid in cell movement, and organize organelles. 4. **Golgi Apparatus (Complex)**: A series of flattened, stacked pouches that modify, package, and sort proteins and lipids for secretion or delivery to other organelles. 5. **Lysosomes and Peroxisomes**: - **Lysosomes**: Contain digestive enzymes to break down waste materials, cellular debris, and foreign invaders. - **Peroxisomes**: Contain enzymes that break down fatty acids and neutralize toxic compounds, producing hydrogen peroxide as a byproduct. 6. **Microvilli**: Tiny finger-like projections on the cell surface that increase surface area to enhance absorption, especially in intestinal cells. 7. **Mitochondria**: The powerhouse of the cell; they generate ATP through cellular respiration. They have a double membrane and their own DNA. 8. **Nucleus**: The control center of the cell, housing DNA and coordinating activities like growth, metabolism, and reproduction. 9. **Nucleolus**: A dense region within the nucleus where ribosomal RNA (rRNA) is synthesized and ribosome assembly begins. 10. **Plasma Membrane**: A selectively permeable phospholipid bilayer that surrounds the cell, controlling the movement of substances in and out. 11. **Ribosome**: The site of protein synthesis. Ribosomes can be free-floating in the cytosol or attached to the rough ER. 12. **Rough Endoplasmic Reticulum (RER)**: Studded with ribosomes; it synthesizes and modifies proteins that are secreted from the cell or sent to the membrane. 13. **Smooth Endoplasmic Reticulum (SER)**: Lacks ribosomes; involved in lipid synthesis, detoxification, and calcium storage. **Know the Steps in Cellular Division & Describe What Happens in Each Stage** **1. Interphase (Preparation for Cell Division)** 1. **G1 Phase (Gap 1)** - **What Happens:** The cell grows in size, produces proteins, and synthesizes organelles. This phase is crucial for normal cell functions, such as metabolism and preparation for DNA replication. - **Key Point:** The cell decides whether to continue to the next phase or enter a resting state (G0 phase). 2. **S Phase (Synthesis Phase)** - **What Happens:** The cell replicates its DNA, ensuring that each daughter cell will have an identical set of chromosomes. The centrosomes (which organize microtubules) are also duplicated. - **Key Point:** Each chromosome now consists of two identical sister chromatids connected by a centromere. 3. **G2 Phase (Gap 2)** - **What Happens:** The cell continues to grow and produces the proteins and organelles needed for cell division. It also checks for DNA replication errors and repairs any damage. - **Key Point:** This phase ensures the cell is fully prepared to enter mitosis. **2. Mitotic Phase (M Phase - Division of the Cell)** **Mitosis** is the division of the nucleus and is followed by **Cytokinesis**, the division of the cytoplasm. Mitosis has four stages: **Prophase, Metaphase, Anaphase,** and **Telophase.** 1. **Prophase** - **What Happens:** - Chromatin condenses into visible chromosomes (each with two sister chromatids). - The nuclear envelope starts to break down. - The mitotic spindle (made of microtubules) begins to form from the centrosomes, which move toward opposite poles of the cell. - **Key Point:** The spindle fibers will later attach to chromosomes to help separate them. 2. **Metaphase** - **What Happens:** - Chromosomes align at the **metaphase plate** (the cell\'s equator). - Spindle fibers from opposite centrosomes attach to the centromeres of each chromosome. - **Key Point:** This alignment ensures that sister chromatids will be evenly divided. 3. **Anaphase** - **What Happens:** - The centromeres split, and the spindle fibers pull the sister chromatids apart toward opposite poles of the cell. - Once separated, each chromatid is considered an individual chromosome. - **Key Point:** This is the phase where chromosomes are physically separated. 4. **Telophase** - **What Happens:** - Chromosomes begin to de-condense back into chromatin. - Nuclear envelopes re-form around the two sets of chromosomes, creating two separate nuclei. - The mitotic spindle disassembles. - **Key Point:** The cell is almost ready to divide completely. 5. **Cytokinesis** (Often overlaps with Telophase) - **What Happens:** - The cytoplasm divides, resulting in two genetically identical daughter cells. - In animal cells, a **cleavage furrow** forms, pinching the cell into two. In plant cells, a **cell plate** forms to separate the two new cells. - **Key Point:** This is the final step of cell division. **Summary of the Cell Cycle Order** 1. **G1 Phase** -- Cell growth and normal functions 2. **S Phase** -- DNA replication 3. **G2 Phase** -- Preparation for mitosis 4. **Mitosis (Prophase → Metaphase → Anaphase → Telophase)** -- Division of the nucleus 5. **Cytokinesis** -- Division of the cytoplasm **Describe the Difference Between Interphase and Mitotic Phase** - **Interphase**: The longest phase, where the cell grows, performs normal functions, and replicates its DNA in preparation for division. No visible chromosomes because the DNA is in a relaxed chromatin state. - **Mitotic Phase**: A shorter phase where the actual division of the nucleus (mitosis) and the cytoplasm (cytokinesis) occurs, leading to the formation of two daughter cells. **Chapter 5: Tissue Organization** **Describe the difference between Exocrine, Apocrine, and Holocrine Glands** 1. **Exocrine glands**: These glands secrete substances onto epithelial surfaces through ducts (e.g., sweat glands, salivary glands, mammary glands). They secrete fluids such as enzymes, mucus, or sweat to specific locations. 2. **Apocrine glands**: These glands release their secretions by pinching off part of the cell\'s cytoplasm (e.g., mammary glands and certain sweat glands). The secretions contain cellular debris and are more viscous than exocrine gland secretions. 3. **Holocrine glands**: These glands release their secretions by rupturing the entire cell, which discharges both the secretion and cell debris (e.g., sebaceous glands). The cells die and are replaced by new ones. **Describe the Common Features of Connective, Epithelial, Neurological, and Muscle Tissues** 1. **Connective Tissue**: Provides structural support, stores energy, and protects organs. It has a lot of extracellular matrix (ECM), and the cells are spaced out. 2. **Epithelial Tissue**: Covers body surfaces, lines cavities, and forms glands. It has closely packed cells with minimal ECM. 3. **Neurological Tissue**: Transmits electrical signals for communication between the body and the brain. It includes neurons and glial cells. 4. **Muscle Tissue**: Responsible for movement. It can contract and is divided into skeletal, smooth, and cardiac types. **Explain the Main Functions of Connective, Epithelial, Neurological, and Muscle Tissues** 1. **Connective Tissue**: Support and bind other tissues, protect organs, store energy (fat), and transport substances (blood). 2. **Epithelial Tissue**: Protects the body, absorbs nutrients, secretes hormones, and facilitates gas exchange. 3. **Neurological Tissue**: Transmits electrical impulses, processes information, and provides support and insulation to neurons. 4. **Muscle Tissue**: Generates movement through contraction. It also maintains posture and generates heat. **Describe the Below Types of Epithelial Tissue and Locations in the Body** 1. **Simple Squamous Epithelium**: Single layer of flat cells. **Location**: Lining blood vessels, alveoli of lungs, and the heart. 2. **Simple Cuboidal Epithelium**: Single layer of cube-shaped cells. **Location**: Kidney tubules, ducts of glands. 3. **Simple Columnar Epithelium**: Single layer of tall cells. **Location**: Lining of the stomach, intestines, and fallopian tubes. 4. **Pseudostratified Columnar Epithelium**: Appears layered, but all cells touch the basement membrane. **Location**: Lining the trachea and upper respiratory tract. 5. **Nonciliated Simple Columnar Epithelium**: Contains microvilli for absorption. **Location**: Digestive tract. 6. **Ciliated Simple Columnar Epithelium**: Contains cilia for movement of substances. **Location**: Lining the bronchi and uterine tubes. 7. **Nonciliated Pseudostratified Columnar Epithelium**: Lacks cilia, typically found in ducts of large glands. **Location**: Male reproductive tract. 8. **Ciliated Pseudostratified Columnar Epithelium**: Has cilia for moving particles. **Location**: Respiratory passages. 9. **Stratified Squamous Epithelium**: Multiple layers of flat cells. **Location**: Skin (keratinized) and mouth (non-keratinized). 10. **Stratified Cuboidal Epithelium**: Multiple layers of cube-shaped cells. **Location**: Sweat glands and mammary glands. 11. **Stratified Columnar Epithelium**: Multiple layers of columnar cells. **Location**: Male urethra and some gland ducts. 12. **Transitional Epithelium**: Cells change shape depending on stretch. **Location**: Urinary bladder and ureters. 13. **Keratinized Epithelium**: Contains keratin, which makes the tissue tough and waterproof. **Location**: Epidermis of the skin. 14. **Non-keratinized Epithelium**: Lacks keratin, remains moist. **Location**: Lining of the mouth, esophagus, and vagina. **Describe the Components of Connective Tissue** 1. **Cells**: The types of cells in connective tissue include fibroblasts, macrophages, mast cells, and adipocytes. 2. **Extracellular Matrix**: Made up of the ground substance and protein fibers. - **Ground Substance**: A gel-like material that fills the space between cells and fibers, containing water, glycoproteins, and proteoglycans. - **Protein Fibers**: - **Elastic Fibers**: Provide elasticity and stretch (e.g., skin, lungs). - **Collagen Fibers**: Provide strength and resist pulling forces (e.g., tendons, ligaments). - **Reticular Fibers**: Form delicate networks to support organs (e.g., lymph nodes, spleen). **Describe the Below Types of Connective Tissue & Know Where They Are Located in the Body** 1. **Connective Tissue Proper**: - **Loose Connective Tissue**: - **Areolar**: Holds organs in place, located under epithelial tissues. - **Adipose**: Stores fat, located beneath the skin and around organs. - **Reticular**: Forms a framework for organs, located in lymph nodes and the spleen. - **Dense Connective Tissue**: - **Dense Regular**: Parallel collagen fibers provide strength, found in tendons and ligaments. - **Dense Irregular**: Collagen fibers in various directions, found in the dermis of the skin. - **Elastic**: Contains elastic fibers, found in the walls of large arteries and lungs. 2. **Supporting Connective Tissue**: - **Cartilage**: - **Hyaline Cartilage**: Smooth surface for movement, found in the nose, ribs, and joints. - **Fibrocartilage**: Provides tensile strength, located in intervertebral discs and menisci. - **Elastic Cartilage**: Flexible, found in the ear and epiglottis. - **Bone**: - **Compact Bone**: Dense and strong, forms the outer layer of bones. - **Spongy Bone**: Less dense, found inside bones (e.g., in the vertebrae). 3. **Fluid Connective Tissue**: - **Blood**: Carries oxygen, nutrients, and waste products. Found in blood vessels. - **Lymph**: Part of the immune system, found in lymphatic vessels. **Describe the Structure, Function, and Location of the Below Muscle Tissues** 1. **Skeletal Muscle**: Striated, voluntary control, multi-nucleated cells.  **Function**: Movement of bones.  **Location**: Attached to bones. 2. **Smooth Muscle**: Non-striated, involuntary control, single nucleus per cell.  **Function**: Moves substances through organs.  **Location**: Walls of hollow organs (e.g., intestines, blood vessels). 3. **Cardiac Muscle**: Striated, involuntary control, and has intercalated discs.  **Function**: Pumps blood.  **Location**: Heart. **Describe the Function, Structure, and Location of Nervous Tissue** 1. **Function**: Transmits electrical impulses for communication, processing information, and controlling body functions. 2. **Structure**: Composed of neurons (nerve cells) and glial cells (supporting cells). 3. **Location**: Found in the brain, spinal cord, and peripheral nerves. **Chapter 6: Integumentary System** **Describe the Structure, Composition, Arrangement, and Function of the 5 Layers of the Epidermis (From Deep to Superficial)** 1. **Stratum Basale (Basal Layer):** - **Structure & Composition:** A single layer of cuboidal to columnar basal cells attached to the basement membrane. - **Arrangement:** Deepest layer, directly above the dermis. - **Function:** Contains stem cells for new keratinocyte production, responsible for cell division, and houses melanocytes and tactile (Merkel) cells. 2. **Stratum Spinosum (Spiny Layer):** - **Structure & Composition:** Several layers of keratinocytes connected by desmosomes, giving a "spiny" appearance under a microscope. - **Arrangement:** Above the stratum basale. - **Function:** Provides strength and flexibility to the skin; contains Langerhans (dendritic) cells for immune response. 3. **Stratum Granulosum (Granular Layer):** - **Structure & Composition:** 3--5 layers of flattened keratinocytes filled with keratohyalin granules and lamellar bodies. - **Arrangement:** Middle layer. - **Function:** Initiates keratinization (cells begin to die and harden), forming a waterproof barrier. 4. **Stratum Lucidum (Clear Layer):** *(Found only in thick skin, e.g., palms, soles)* - **Structure & Composition:** Thin, translucent layer of dead keratinocytes. - **Arrangement:** Between the stratum granulosum and corneum. - **Function:** Provides extra protection and reduces friction. 5. **Stratum Corneum (Horny Layer):** - **Structure & Composition:** 20--30 layers of dead, flattened, anucleated keratinocytes filled with keratin. - **Arrangement:** Outermost layer. - **Function:** Acts as a protective barrier against environmental damage, water loss, and pathogens. **Describe the Three Types of Cells that occupy the Stratum Basale** 1. **Keratinocytes:** - **Function:** Produce keratin, a protein that strengthens the skin and makes it water-resistant. - **Role:** Constantly divide to replenish the upper layers. 2. **Melanocytes:** - **Function:** Produce melanin, the pigment responsible for skin color. - **Role:** Protects against UV radiation by absorbing harmful rays. 3. **Tactile (Merkel) Cells:** - **Function:** Sensory receptors for light touch. - **Role:** Found in areas with high sensory function like fingertips. **Describe the Epidermal Dendritic (Langerhans) Cells and Explain in the Body Where They Are Located** - **Function:** Act as immune cells that detect and respond to pathogens. They phagocytize (engulf) foreign particles and present antigens to immune cells. - **Location:** Found mainly in the stratum spinosum but also present in other epidermal layers. **Describe the Structure, Organization, and Functions of the Layers of the Dermis** 1. **Papillary Layer:** - **Structure:** Composed of loose areolar connective tissue. - **Organization:** Contains dermal papillae (finger-like projections) that interlock with the epidermis. - **Functions:** Provides nutrients to the epidermis, houses capillaries, Meissner's corpuscles (touch receptors), and free nerve endings. 2. **Reticular Layer:** - **Structure:** Dense irregular connective tissue with thick collagen and elastic fibers. - **Organization:** Deeper, larger portion of the dermis. - **Functions:** Provides strength, elasticity, and houses structures like hair follicles, sweat glands, sebaceous glands, and blood vessels. **Describe the Structures Found Within the Dermis** 1. **Apocrine Sweat Gland:** Produces thick, odorous sweat in areas like armpits and groin; active during stress or sexual arousal. 2. **Arrector Pili Muscle:** Small smooth muscle attached to hair follicles; causes "goosebumps" when it contracts. 3. **Artery:** Carries oxygenated blood to the skin. 4. **Capillary Network:** Supplies nutrients and oxygen to the epidermis and removes waste. 5. **Hair:** A filament of keratinized cells growing from a follicle in the dermis. 6. **Hair Root/Follicle Plexus:** A network of nerve endings around the hair follicle that senses hair movement. 7. **Meissner's Corpuscle:** Touch receptors located in the papillary dermis, sensitive to light touch. 8. **Merocrine (Eccrine) Sweat Gland:** Produces watery sweat for thermoregulation; found all over the body. 9. **Nerve Ending (Free):** Detects pain, temperature, and mechanical stimuli. 10. **Pacinian Corpuscle:** Deep pressure and vibration receptors found in the reticular dermis. 11. **Papilla:** The dermal papilla at the base of the hair follicle contains capillaries that nourish growing hair. 12. **Sebaceous Gland:** Secretes sebum (oil) to lubricate and waterproof the skin and hair. 13. **Vein:** Returns deoxygenated blood from the skin back to the heart. **Describe the structure and Function of the Subcutaneous Layer (Hypodermis)** - **Structure:** Composed of loose connective tissue and adipose tissue. - **Function:** Provides insulation, energy storage, cushioning, and anchors the skin to underlying muscles. **Describe the Three Zones of Hair Structure** 1. **Hair Bulb:** - **Structure:** The swollen base of the hair, surrounding the dermal papilla. - **Function:** Site of hair growth where living cells divide. 2. **Hair Root:** - **Structure:** The portion of the hair beneath the skin, within the follicle. - **Function:** Anchors the hair and continues to grow as cells keratinize. 3. **Hair Shaft:** - **Structure:** The visible part of the hair above the skin's surface. - **Function:** Provides protection and plays a role in sensory perception.