1st Semester - 1st Year Nursing Anatomy and Physiology PDF

ANATOMY AND PHYSIOLOGY Professor Bernard S. Barranco RN, MAN, Ed.D MIDTERMS TOPIC OUTLINE Skeletal System I. PRELIMS...

ANATOMY AND PHYSIOLOGY Professor Bernard S. Barranco RN, MAN, Ed.D MIDTERMS TOPIC OUTLINE Skeletal System I. PRELIMS Composed of bones and joints, providing structure A. The Human Body: Overview and support. B. Cells and Tissues Muscular System a. Part I - Cells b. Part II - Body Tissues Allows movement through muscle contraction. C. Integumentary System Nervous System II. MIDTERMS Controls body functions and responses to stimuli. A. The Skeletal System Endocrine System B. The Muscular System C. The Nervous System Glands that release hormones, regulating body III. FINALS processes like growth and metabolism. IV. REFERENCES Cardiovascular System V. TRANS AUTHORSHIP *note new topics will be colored dark blue Heart and blood vessels that transport oxygen, nutrients, and waste. Lymphatic System Supports immune function and fluid balance. Respiratory System THE HUMAN BODY: OVERVIEW Includes lungs and airways, facilitating breathing ANATOMY AND PHYSIOLOGY DEFINITION and gas exchange. Anatomy Digestive System The study of the body's structure and its parts. It can Breaks down food, absorbing nutrients and be divided into: expelling waste. A. Gross Anatomy: Examining large, visible structures Urinary System like bones and muscles. Removes nitrogenous waste from the blood, B. Microscopic Anatomy: Studying structures that maintaining fluid balance. need a microscope, like cells and tissues. Reproductive System Physiology Produces offspring and regulates sexual function. Focuses on how these body parts function, such as ESSENTIAL BODY FUNCTION how the heart pumps blood or how the lungs facilitate 1. Movement: Controlled by the muscular and skeletal breathing. LEVELS OF ORGANIZATION IN THE BODY systems, allowing us to move and interact with our 1. Chemical Level: Atoms combine to form molecules. environment. 2. Cellular Level: Molecules form cells, the smallest unit 2. Responsiveness: The nervous system detects and of life. responds to internal and external changes. 3. Tissue Level: Similar cells work together to perform a 3. Digestion: The digestive system breaks down food common function. into nutrients, which are transported to cells by the 4. Organ Level: Tissues combine to form organs (e.g., cardiovascular system. the heart), which perform specific functions. 4. Metabolism: All chemical reactions in the body, 5. Organ System Level: Groups of organs that work including breaking down nutrients for energy and together to perform complex functions (e.g., the building necessary compounds. cardiovascular system). 5. Excretion: The removal of waste products, managed 6. Organismal Level: All organ systems combined by the urinary, digestive, and integumentary systems. make up the whole organism. 6. Reproduction: Producing new cells and offspring, BODY SYSTEMS OVERVIEW regulated by the reproductive and endocrine systems. Integumentary System Includes skin, hair, and nails, protecting the body. PADAYON FUTURE RN!!!, LABOR OMNIA VINCIT  7. Growth: Increase in body size or cell number, Example: "The bladder is inferior to the regulated by hormones kidneys." 5. Medial: Refers to being closer to the midline of the THE LANGUAGE OF ANATOMY body. Special terminology is used to prevent misunderstanding. Example: "The heart is medial to the lungs." Exact terms are used for: 6. Lateral: Refers to being farther from the midline of the 1. Position body. 2. Direction Example: "The ears are lateral to the eyes." 3. Regions 4. Structures 7. Proximal: Describes a position closer to the point of Anatomical Position attachment or the trunk of the body. Typically used in The standard body position used to describe reference to limbs. locations and directions (standing erect, palms facing Example: "The knee is proximal to the forward). ankle." 8. Distal: Describes a position farther from the point of attachment or the trunk. Example: "The fingers are distal to the shoulder." 9. Superficial (External): Refers to a position closer to the surface of the body. Example: "The skin is superficial to the muscles." 10. Deep (Internal): Refers to a position farther away Directional Terminology from the surface of the body. 1. Anterior (Ventral): Refers to the front of the body or body part. Example: "The sternum is anterior to the heart." 2. Posterior (Dorsal): Refers to the back of the body or body part. Example: "The kidneys are posterior to the intestines." 3. Superior (Cranial or Cephalic): Indicates a position toward the head or above another part. Example: "The lungs are superior to the liver." 4. Inferior (Caudal): Indicates a position away from the head or below another part. 2 Example: "The lungs are deep to the ribcage." 3  BODY PLANES AND SECTIONS some reproductive organs, and the rectum. It is positioned below the abdominal cavity. Sagittal Plane: Divides the body into right and left parts. Frontal (Coronal) Plane: Divides the body into anterior (front) and posterior (back) parts. Transverse Plane: Divides the body into superior (upper) and inferior (lower) parts. ABDOMINOPELVIC QUADRANTS BODY CAVITIES Right Upper Quadrant (RUQ): Includes the liver, Dorsal Body Cavities located along the back (posterior) side of the body. It is divided into two main gallbladder, part of the stomach, and part of the small sub-cavities: and large intestines. Left Upper Quadrant (LUQ): Contains the stomach, a. Cranial Cavity: This is the space inside the spleen, pancreas, and part of the liver and intestines. skull that houses the brain. It provides protection to the brain, encased by the cranial Right Lower Quadrant (RLQ): Houses the appendix, bones. part of the small intestine, right ovary (in females), and b. Spinal (or Vertebral) Cavity: This cavity runs down the back and contains the spinal cord. It right ureter. is formed by the vertebral column (spine), Left Lower Quadrant (LLQ): Contains parts of the protecting the spinal cord from injury. small intestine, left ovary (in females), and left ureter. Ventral Body Cavity The ventral body cavity is located along the front (anterior) side of the body and is much larger than the dorsal cavity. It is subdivided into: a. Thoracic Cavity: This cavity is located above the diaphragm and houses the heart and lungs. It is further divided into: b. Pleural Cavities: Two cavities surrounding each lung. c. Mediastinum: A central region that includes the heart, esophagus, trachea, and major blood vessels. The heart is specifically enclosed within the pericardial cavity. d. Abdominopelvic Cavity: Located below the diaphragm, this cavity is further divided into: e. Abdominal Cavity: Contains digestive organs like the stomach, liver, spleen, pancreas, small intestine, and most of the large intestine. f. Pelvic Cavity: Houses the urinary bladder, 4  ABDOMINOPELVIC REGIONS Right Hypochondriac Region: Contains part of the liver, gallbladder, and right kidney. Epigastric Region: Located above the stomach; includes the stomach, part of the liver, and pancreas. Left Hypochondriac Region: Includes part of the stomach, spleen, and left kidney. Right Lumbar Region: Contains parts of the large intestine and right kidney. HOMEOSTASIS Umbilical Region: Center of the abdomen; houses the small intestine and part of the large intestine. The body’s ability to maintain stable internal conditions despite external changes. This involves: Left Lumbar Region: Contains parts of the small and ○ Receptor: Senses changes in the large intestines, and left kidney. environment. ○ Control Center: Analyzes information and Right Iliac (Inguinal) Region: Includes the appendix decides the response. and part of the large intestine. ○ Effector: Implements the response to restore Hypogastric (Pubic) Region: Located below the balance. Feedback Mechanisms: umbilical region; contains the bladder, part of the small ○ Negative Feedback: Reduces the effect of a intestine, and reproductive organs. stimulus (e.g., body temperature regulation). Left Iliac (Inguinal) Region: Contains part of the large ○ Positive Feedback: Increases the effect of a stimulus (e.g., blood clotting). intestine and, in females, part of the reproductive organs. 5  CELLS AND TISSUES PART I: CELLS Cell Theory and Structure Cell Theory: 1. Basic Unit: A cell is the basic structural and functional unit of living organisms. 2. Organism Activity: The activity of an organism depends on the collective activities of its cells. 3. Subcellular Structures: The activities of cells are dictated by their specific subcellular structures (Principle of Complementarity). 4. Continuity of Life: New cells arise only from existing cells, ensuring the continuity of life. Plasma Membrane Chemical Composition of Cells A flexible, transparent barrier that encloses cell contents and separates them from the external Primary Elements: Cells are mainly composed of four environment. elements: Carbon (C), Oxygen (O), Hydrogen (H), and Nitrogen (N). Functions: Water Content: H2O constitutes approximately 60% of cell content, playing a crucial role in cellular processes. Regulates the movement of substances into and out of the cell. ANATOMY OF A GENERALIZED CELL Maintains cell integrity and facilitates cell communication. A generalized cell consists of three main regions: the nucleus, plasma membrane, and cytoplasm. Structure: Composed of a double layer of phospholipid molecules arranged "tail to tail." Nucleus Phospholipid Head: Polar and hydrophilic The nucleus contains DNA, which is essential for cell (water-attracting). reproduction, regulation, and hereditary information. Phospholipid Tails: Nonpolar and hydrophobic (water-repelling). Structure: Proteins: Embedded proteins function as enzymes, receptors, Nuclear Envelope/Nuclear Membrane: A double and channels for transport. membrane surrounding the nucleus. ○ Nuclear Pores: Allow exchange of material between the nucleus and cytoplasm. ○ Nucleoplasm: A gel-like substance within the nucleus, housing the nucleolus and chromatin. Nucleolus: A dense region involved in ribosome production. Chromatin: DNA and protein complex that condenses to form chromosomes during cell division. 6  Cytoplasm The cytoplasm is the cellular material between the nucleus and the plasma membrane. Components: Cytosol: A semi-fluid substance that contains dissolved nutrients, ions, and other substances. Organelles: Specialized structures that perform specific functions within the cell. Inclusions: Non-functional, stored nutrients, and cell products. Cytoplasmic Extensions Cilia: Short, hair-like projections that move substances across cell surfaces. Flagella: Longer extensions that propel the cell, such as the tail of a sperm cell. Microvilli: Finger-like projections that increase the surface area for absorption. Cytoplasm Organelles 1. Mitochondria: The powerhouse of the cell, producing ATP through cellular respiration. 2. Ribosomes: Sites of protein synthesis, found floating in the cytoplasm or attached to the rough ER. Endoplasmic Reticulum (ER): Rough ER: Studded with ribosomes; involved in protein synthesis and transport. Smooth ER: Lacks ribosomes; involved in lipid synthesis, detoxification, and calcium storage. 3. Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for storage or transport out of the cell. 4. Lysosomes: Contain digestive enzymes to break down waste materials and cellular debris. 5. Peroxisomes: Detoxify harmful substances and break down fatty acids. 6. Cytoskeleton: Provides structural support, maintains cell shape, and facilitates movement. 7. Centrioles: Involved in organizing microtubules during cell division. 7  CELL DIVERSITY Cells vary in shape, size, and function based on their roles in the Active Processes: Require energy (ATP). body: 1. Active Transport: Movement of molecules against a 1. Cells that Connect Body Parts: concentration gradient using transport proteins; e.g., ○ Fibroblasts: Produce fibers for connective Sodium-Potassium Pump. tissue. 2. Vesicular Transport: Involves the movement of large ○ Erythrocytes (Red Blood Cells): Transport particles or fluids via vesicles. oxygen. ○ Exocytosis: Transport out of the cell. 2. Cells that Cover and Line Body Organs: ○ Endocytosis: Transport into the cell (e.g., ○ Epithelial Cells: Form protective barriers and phagocytosis, pinocytosis). linings. 3. Cells that Move Organs and Body Parts: ○ Skeletal Muscle Cells: Contract to move bones. ○ Smooth Muscle Cells: Contract to move internal organs. 4. Cells that Store Nutrients: ○ Fat Cells (Adipocytes): Store lipids for energy. 5. Cells that Fight Disease: ○ Macrophages: Engulf and digest pathogens. 6. Cells that Gather Information and Control Body Functions: ○ Nerve Cells (Neurons): Transmit electrical impulses. 7. Cells of Reproduction: ○ Oocytes (Female) *Largest Cell: Egg cells. ○ Sperm Cells (Male): Male reproductive cells. CELL PHYSIOLOGY Membrane Transport: The plasma membrane regulates what enters and exits the cell. Intracellular Fluid: Combination of nucleoplasm and cytosol containing dissolved gases, nutrients, and salts. Interstitial Fluid: Fluid surrounding the cells, containing nutrients and waste products. Transport Mechanisms Passive Processes: Do not require cellular energy; Adenosine Triphosphate (ATP). 1. Diffusion: Movement of molecules from a region of higher concentration to lower concentration. 2. Filtration: Movement across a membrane due to a pressure gradient; non-selective, as seen in the kidneys. 3. Osmosis: Movement of water through a selectively permeable membrane. Hypertonic Solution: Higher solute concentration outside the cell, causing the cell to shrink. Hypotonic Solution: Lower solute concentration outside the cell, causing the cell to swell. 8  PART II: BODY TISSUES The human body is composed of four primary tissue types, each with specific functions. Pseudostratified Columnar Epithelium: Appears Four Primary Tissue Types layered due to cell nuclei at varying heights, but is actually a single layer; involved in secretion and movement of mucus (e.g., respiratory tract). 1. Epithelial Tissue: Covers body surfaces, lines cavities, and forms glands. 2. Connective Tissue: Supports, binds, and protects Stratified Epithelia: other tissues. 3. Nervous Tissue: Transmits electrical impulses, Stratified Squamous Epithelium: Multiple layers of coordinating body functions. flat cells; protects underlying tissues from abrasion 4. Muscle Tissue: Produces movement through (e.g., skin, mouth). contraction. Stratified Cuboidal Epithelium: Typically two layers of cube-like cells; involved in protection (e.g., ducts of sweat glands). Stratified Columnar Epithelium: Rare, consists of multiple layers of columnar cells; involved in protection and secretion (e.g., male urethra). Transitional Epithelium: Multiple layers of cells that can stretch; lines the bladder and allows it to expand and contract. Glandular Epithelium: Specialized epithelial cells that form Epithelial Tissue glands. General Characteristics: Endocrine Glands: Ductless glands that secrete hormones directly into the bloodstream (e.g., thyroid gland). Covers and lines organs and the body. Exocrine Glands: Glands that secrete their products Forms a protective barrier. into ducts (e.g., sweat glands, salivary glands). Avascular (lacks blood vessels) but innervated (has nerve supply). Has a high rate of regeneration due to frequent cell division. Cells are tightly packed with minimal extracellular material. Classification: Based on Cell Arrangement: Simple (one layer) or stratified (multiple layers). Based on Cell Shape: Squamous (flat), cuboidal (cube-like), and columnar (tall). Types of Epithelial Tissue Simple Epithelia: Simple Squamous Epithelium: Single layer of flat cells; allows for diffusion and filtration (e.g., in the lungs and blood vessels). Simple Cuboidal Epithelium: Single layer of cube-shaped cells; involved in secretion and absorption (e.g., in glands and kidney tubules). Simple Columnar Epithelium: Single layer of tall, column-like cells; specialized for absorption and secretion (e.g., lining of the stomach and intestines). Goblet cells, which produce a lubricating mucus, are often seen in this type of epithelium. 9  Connective Tissue General Characteristics: Connective tissues provide support and bind other tissues together. They have a rich supply of blood vessels (except for cartilage). Contain an extracellular matrix that consists of ground substance and fibers. Connective Tissue Cells Connective tissues provide support and bind other tissues together. They have a rich supply of blood vessels (except for Components of Connective Tissue cartilage). Contain an extracellular matrix that consists of ground substance and fibers. The Extracellular Matrix is a complex network of macromolecules, mainly proteins and carbohydrates, that Fibroblasts: Produce fibers (collagen, elastic, reticular) occupy the space between cells in connective tissues. It is and ground substance. composed of two main components: the ground substance and protein fibers. Ground Substance: Fills the space between cells and fibers; consists of water, proteins, and polysaccharides. Fibers: ○ Collagen Fibers: Strong and flexible; provide tensile strength. ○ Elastic Fibers: Stretchable and resilient; provide elasticity. ○ Reticular Fibers: Thin and branching; form supportive networks. Mast Cells: Release histamine and other chemicals during inflammatory and allergic responses. Macrophages: Engulf and digest pathogens, dead cells, and debris. 10  Types of Connective Tissue Muscle Tissue Loose Connective Tissue: Muscle tissues are specialized for contraction, which brings about movement. Areolar Tissue: Loose arrangement of fibers and cells; cushions and binds organs. Types of Muscle Tissue: Adipose Tissue: Stores fat for energy, insulation, and 1. Skeletal Muscle: cushioning. Location: Attached to bones. Reticular Tissue: Forms a network that supports other Voluntary control: Contractions are cells (e.g., in lymph nodes, spleen). consciously controlled. Striated appearance: Due to the Dense Connective Tissue: arrangement of actin and myosin filaments. In dense connective tissue, also called dense fibrous Function: Enables body movement, tissue Dense connective tissue forms strong, ropelike facial expressions, and posture. structures such as tendons and ligaments. Structure: Elongated, cylindrical cells Tendons attach skeletal muscles to bones; ligaments with multiple nuclei. connect bones to bones at joints. 2. Smooth Muscle: Ligaments are more stretchy and contain more elastic Location: Walls of hollow organs fibers than do tendons. (e.g., stomach, intestines, blood Dense connective tissue also makes up the lower vessels). layers of the skin (dermis), where it is arranged in Involuntary control: Contractions sheets. are not consciously controlled. Non-striated appearance: Lacks the striations seen in skeletal muscle. Cartilage: Firm but flexible tissue that provides support and Function: Moves substances through cushioning. organs (e.g., peristalsis in the intestines), regulates blood vessel Hyaline Cartilage: Most common type; found in joints, diameter. nose, and respiratory passages. Structure: Spindle-shaped cells with Elastic Cartilage: Contains more elastic fibers; found a single nucleus. in the ear and epiglottis. Fibrocartilage: Contains dense collagen fibers; found in intervertebral discs and knee menisci. 3. Cardiac Muscle: Bone (Osseous Tissue): Rigid connective tissue that supports Location: Found only in the heart. and protects organs; contains a hard matrix of collagen fibers Involuntary control: Contractions and calcium salts. are not consciously controlled. Striated appearance: Similar to Blood: A fluid connective tissue that transports nutrients, gases, skeletal muscle but with a unique and waste products throughout the body. branching structure. Function: Pumps blood throughout Nervous Tissue the body. Structure: Cells are branched, have Found in the brain, spinal cord, and peripheral nerves. a single nucleus, and are connected by intercalated discs that allow Components: synchronized contraction. Neurons: Nerve cells responsible for transmitting electrical impulses. They have three main parts: the cell body, dendrites (receive signals), and axons (transmit signals). Neuroglia: Support cells that provide physical support, insulation, and nutrients to neurons. They outnumber neurons and play essential roles in maintaining the environment around neurons. 11  connective tissue. The two layers include the parietal layer (lining the cavity walls) and the visceral layer INTEGUMENTARY SYSTEM (covering the organs). These layers are separated by a small amount of serous fluid. BODY MEMBRANES Function: Reduces friction between moving organs by Functions: producing serous fluid, allowing organs to move smoothly within their respective cavities (e.g., lung Cover body surfaces. expansion, heart contraction). Provides protection and Line body cavities. support for internal organs. Form protective sheets around organs. Connective Tissue Membranes Two Major Groups: Synovial Membrane: 1. Epithelial Membranes: ○ Cutaneous Membrane. Structure: ○ Mucous Membrane. ○ Composed of soft areolar connective tissue ○ Serous Membrane. without epithelial cells. 2. Connective Tissue Membrane: Location: ○ Synovial Membrane. ○ Found lining the fibrous capsules surrounding joints, as well as bursae and tendon Parts of the Epithelial Membrane sheaths. Function: 1. Cutaneous Membrane ○ Produces synovial fluid, which acts as a lubricant, reducing friction between moving Location: Covers the entire external surface of the bones and cushioning joints. body. Structure: Composed of a keratinized stratified INTERACTIONS WITH THE INTEGUMENTARY SYSTEM squamous epithelium (epidermis) overlying a thick layer of dense irregular connective tissue (dermis). The Functions of the Skin: epidermis contains keratinocytes that produce keratin, providing waterproofing and protection. ○ Keeps water and valuable molecules in the Function: Acts as a protective barrier against physical body. damage, pathogens, and water loss. Regulates body ○ Pliable yet tough, providing protection from: temperature, excretes waste through sweat, and plays Mechanical damage: Bumps and a key role in sensory perception. cuts. Chemical damage: Acids and bases. Thermal damage: Heat and cold. 2. Mucous Membranes (Mucosae) Ultraviolet damage: Sunlight. Microorganisms: Bacteria and Location: Line body cavities and tubes that open to the viruses. exterior, such as the digestive, respiratory, urinary, and ○ Desiccation prevention: The skin contains reproductive tracts. keratin and glycolipids to prevent water loss. Structure: Composed of an epithelial layer (stratified squamous, simple columnar, or pseudostratified Protection Mechanism of the Skin columnar) overlying a layer of loose connective tissue (lamina propria). Contains goblet cells that secrete mucus. Mechanical Damage: Function: Protects underlying tissues, traps pathogens and particles, keeps surfaces moist, and aids in Keratin toughens skin cells, providing a durable barrier. absorption and secretion. Pressure receptors in the skin alert the nervous Types of Epithelium: system to pressure or potential injury. - Stratified squamous epithelium: Found in the mouth and esophagus. Chemical Damage: - Simple columnar epithelium: Found in the digestive tract. Keratinized cells form an impermeable barrier that prevents harmful substances from penetrating the skin. 3. Serous Membranes (Serosae) Pain receptors alert the body to chemical exposure. Location: Line closed internal body cavities and cover the organs within these cavities, such as the thoracic (lungs), pericardial (heart), and abdominal (digestive organs) cavities. Structure: Composed of two layers— a thin epithelial layer (mesothelium) overlying a layer of loose 12 Thermal Damage: Integumentary System and Circulatory System: The skin contains heat and cold receptors that detect Thermoregulation: Blood vessels in the skin help temperature changes, protecting the body from extreme control body temperature. When the body is hot, blood heat or cold. vessels dilate to increase blood flow to the skin, releasing heat. When the body is cold, blood vessels Ultraviolet Damage: constrict to retain heat. Oxygen and Nutrient Supply: The circulatory system Melanin produced by melanocytes absorbs and provides oxygen and nutrients to skin cells. protects against UV radiation. Integumentary System and Skeletal System: Microorganism Protection: Vitamin D Synthesis: The skin produces vitamin D, Acid Mantle: The skin's acidic secretions inhibit which is essential for calcium absorption in the bacterial growth. intestines. This strengthens bones by ensuring they Phagocytes: These cells in the skin engulf and destroy receive enough calcium for growth and repair. foreign invaders. Integumentary System and Muscular System: Temperature Regulation: When the body is cold, Thermoregulation muscles (like arrector pili) contract, causing hairs to stand up, creating warmth through goosebumps. Support for Movement: Skin stretches and flexes with Body Heat Loss: body movements, facilitated by the subcutaneous layer. The body cools down by activating sweat glands and Integumentary System and Respiratory System: allowing blood to flow into the skin capillaries. Protection: Hairs in the nasal cavity filter dust and Heat Retention: particles from the air before it enters the lungs. Thermoregulation: The respiratory system works with Blood flow to the skin is restricted to prevent heat loss. the skin to regulate body temperature through sweat and increased breathing during exercise. Other Functions of the Integumentary System Integumentary System and Digestive System: Excretion: The skin excretes urea, uric acid, and other wastes through perspiration. Vitamin D Absorption: Vitamin D synthesized by the skin enhances the absorption of calcium and Vitamin D Synthesis: Modified molecules in the skin are phosphorus in the digestive tract, essential for strong converted to vitamin D by UV exposure from sunlight. bones and teeth. Liver: Metabolizes vitamin D into its active form, which INTERACTIONS WITH OTHER SYSTEMS then aids in calcium absorption. Integumentary System and Nervous System: Integumentary System and Urinary System: Sensory Receptors: The skin contains sensory Excretion: The skin helps the kidneys by excreting receptors for touch, pressure, pain, and temperature, waste products such as urea and salts through sweat, which relay information to the brain through the nervous reducing the load on the urinary system. system. Water Balance: Works with the kidneys to maintain the Temperature Regulation: The nervous system body's water balance through perspiration. controls the dilation and constriction of blood vessels in the skin and the activity of sweat glands for Integumentary System and Endocrine System: thermoregulation. Hormonal Effects: Hormones, especially from the Integumentary System and Immune System: endocrine system (such as sex hormones and thyroid hormones), influence the skin’s oil production, hair Skin as a Barrier: The skin is the first line of defense growth, and the distribution of subcutaneous fat. against pathogens. Melanin Production: Melanin production can be Langerhans Cells: Specialized immune cells in the affected by hormones like MSH (melanocyte-stimulating epidermis detect and fight off invading pathogens. hormone). Acid Mantle: Skin secretions are acidic, inhibiting bacterial growth. 13  Dermis: Structure: Made of dense connective tissue, tear-resistant. Papillary layer: ○ Contains dermal papillae, capillary loops, and sensory receptors. Reticular layer: ○ Contains collagen and elastic fibers, providing STRUCTURES OF THE SKIN strength and elasticity. Epidermis: Avascular: No direct blood supply. Made of keratinocytes, cells that produce keratin, a tough protein. Layers: ○ Stratum corneum: Outermost layer, consisting of dead keratinized cells. ○ Stratum lucidum: Found only in thick skin (e.g., palms, soles). ○ Stratum granulosum: Contains keratohyalin granules, a precursor to keratin, which are involved in the formation of the waterproof barrier. ○ Stratum spinosum: Provides structural strength. This layer also contains Langerhans cells, which are part of the immune system. ○ Stratum germinativum (basale): Deepest layer, actively dividing cells. This layer also Hypodermis (Subcutaneous Layer): contains melanocytes (cells producing melanin) and Merkel cells (associated with sensory nerve endings). Structure: Composed of elastic areolar and adipose tissue. Function: ○ Anchors skin to underlying organs, acts as a shock absorber, and provides insulation. 14  granulation tissue. 3. Scar Formation: Fibroblasts produce scar tissue, and SKIN COLOR DETERMINANTS the clot disintegrates. 4. Scar Strengthening: Scar tissue strengthens, and a raised keloid may form. Melanin: A pigment produced by melanocytes that ranges from yellow to brown to black. EFFECTS OF AGING ON THE SKIN Function: Absorbs UV rays, protecting underlying tissue from sun damage. Thinning of the epidermis. Reduced numbers of Langerhans cells Carotene: An orange-yellow pigment found in the stratum (immune cells). corneum and subcutaneous tissues. Decreased production of vitamin D3. Decreased melanocyte activity, leading to paler skin. Source: Carotene is obtained from food and deposited Reduced glandular activity, resulting in drier in the skin. skin. Reduced blood supply, leading to slower Hemoglobin: Found in red blood cells and gives a reddish hue healing. to fair skin. Decreased function of hair follicles and elastic fibers, causing sagging. Hormonal changes that slow repair processes. APPENDAGES OF THE SKIN 1. Cutaneous Glands: Sebaceous (Oil) Glands: ○ Found all over the skin except for palms and soles. ○ Secrete sebum (oily substance) into hair follicles. ○ Function: Lubricates the skin, prevents drying, and has antibacterial properties. Skin Color Changes and Diseases Associated with It Sweat (Sudoriferous) Glands: ○ Eccrine glands: Found all over the body, Redness (Erythema): Caused by embarrassment, produce sweat to regulate temperature. fever, hypertension, inflammation, or allergies. ○ Apocrine glands: Found in axillary and genital regions, larger than eccrine glands, and activated during stress or sexual arousal. Pallor (Blanching): Caused by emotional stress, These glands secrete fatty acids and proteins, anemia, low blood pressure, or impaired blood flow. which bacteria feed on, leading to body odor. Jaundice: Yellow skin resulting from liver disorders. Bruises (Hematomas): Occur when blood pools in tissues after trauma. Addison’s Disease: Causes a bronze or darkened skin tone. Vitiligo: Results in the loss of skin pigment in patches. WOUND HEALING PROCESS 1. Bleeding: Triggered by injury, with mast cells initiating an inflammatory response. 2. Scab Formation: The scab stabilizes and protects the wound. Inflammatory Response: Germinative cells migrate around the wound. Macrophages clean the area. Fibroblasts and endothelial cells move in, producing 15  Texture: Influenced by the shape of the hair shaft: Oval Shaft: Produces smooth, silky, and wavy hair. Flat, Ribbon-like Shaft: Produces curly and kinky hair. Round Shaft: Produces straight and coarse hair. 2. Hair: Structure: ○ Hair is produced by hair follicles and consists 3. Nails: of keratinized cells. Structure: ○ The hair shaft is the visible part, while the hair ○ Composed of keratinized epithelial cells. root is embedded in the skin. ○ Free edge: The part that extends beyond the ○ The arrector pili muscle attached to the finger or toe. follicle contracts to make the hair stand up ○ Nail body: The visible attached portion. (goosebumps). ○ Nail root: Embedded in the skin. Function: Provides protection and insulation. ○ Lunula: The white crescent at the base of the nail. Composition: Made up of three layers: ○ Cuticle: The skin folds at the base of the nail. Medulla: The central core of the hair, composed of flexible, soft keratin. Cortex: Surrounds the medulla and is composed of several layers of cells containing hard keratin, providing strength and color to the hair. Cuticle: The outermost layer, consisting of a single layer of overlapping, hard keratinized cells. It protects the inner layers and contributes to the hair’s shine. Hair Growth Cycle: Anagen Phase: The active growth phase, where cells in the hair bulb rapidly divide and produce the hair shaft. This phase can last several years. Catagen Phase: The transitional phase where hair growth slows, and the follicle shrinks. This phase lasts a few weeks. Telogen Phase: The resting phase where hair growth stops, and the hair shaft is fully formed. This phase lasts a few months before the hair falls out and a new anagen phase begins. 16  SKIN LIFE CYCLE Cell turnover: It takes 15–30 days for a cell to move from the stratum germinativum to the stratum corneum, where it becomes part of the outer layer of dead cells. These cells are eventually shed. 17  SKELETAL SYSTEM Osteon THE FUNCTION OF BONES The osteon is the functional unit of compact bone. First studied by Clopton Havers in 1691, it is a cylindrical structure composed Bones serve essential functions in the body: of concentric rings called lamellae, which surround a central canal. 1. Support: Provide structural support for the entire body. 2. Protection: Protect vital organs like the brain, heart, Lamellae: Rings of the extracellular matrix that and lungs. provide strength to the bone, composed of organic and 3. Movement: Act as levers that allow movement in inorganic materials. conjunction with muscles. ○ Types of Lamellae: 4. Storage: Store minerals such as calcium and fats. 1. Interstitial Lamellae: Fill spaces 5. Blood Cell Formation: Bone marrow is responsible for between osteons. producing red and white blood cells. 2. Circumferential Lamellae: Encircle the entire bone. THE SKELETAL SYSTEM 3. Concentric Lamellae: Surround the central canal. Lacunae: Small spaces within the lamellae that contain The term "skeleton" comes from the Greek word meaning osteocytes, the mature bone cells responsible for "dried-up body." Despite appearing dry, bones are actually living maintaining the bone matrix. tissues. A human newborn has about 350 bones, which fuse Canals: together over time, leaving adults with 206 bones. In adults, the ○ Central (Haversian) Canal: Runs parallel to skeleton weighs approximately 30 pounds. the bone’s length, containing blood vessels, lymph vessels, and nerves. Types of Bone Tissue ○ Perforating (Volkmann’s) Canals: Run perpendicular to the central canals, connecting There are two main types of bone tissue: them. Compact Bone: ○ Dense, strong tissue that provides structural support. ○ Covered by the periosteum, where muscles and tendons attach. Spongy Bone: ○ Also called cancellous bone, located inside bones. ○ Made up of slender fibers and lamellae, filled with marrow that produces red blood cells. ○ Provides flexibility and absorbs shock, storing essential minerals, such as 99% of the body’s calcium. GROSS ANATOMY OF A BONE Diaphysis: The shaft of long bones, composed mainly of compact bone. It houses the medullary cavity, which contains yellow marrow (fat) in adults. Epiphysis: The ends of long bones, made primarily of spongy bone. Infants: Have red marrow, which produces blood cells. Adults: Red marrow is limited to areas like the hip bones and ends of long bones. Epiphyseal Growth Plate: Contains hyaline cartilage that allows bone growth in children. Once growth stops, the cartilage is 18 replaced by bone, forming an epiphyseal line. BONE GROWTH AND REMODELING Periosteum: A fibrous outer membrane that contains blood In embryos, most of the skeleton is made of hyaline cartilage, vessels, nerves, and serves as an attachment point for tendons which is gradually replaced by bone through a process called and ligaments. ossification. In children, bones grow in length through the epiphyseal plates (Epiphyseal Disc), where cartilage is Articular Cartilage: Made of hyaline cartilage, covering joint replaced by bone. Bones grow longitudinally for height and surfaces to reduce friction and absorb shock. laterally (appositional growth) to support body weight. Arteries: Supply bone cells with nutrients Bone remodeling is a process by both osteoblasts and osteoclasts. To retain normal proportions and strength during long bone growth (increase in body size and weight) In response to: Calcium Ion in the blood Pull of gravity and muscle on the skeleton A combined action of osteoblasts (bone forming cells) and osteoclasts (bone destroying cells) Osteoblasts deposit bone on the external bone surface (like a brick layer) Osteoclasts break down bone from the inside Bone Cells Osteocytes: Mature bone cells that maintain bone tissue. Osteoblasts: Cells that form new bones (Secretes extracellular matrix). Osteoclasts: Cells responsible for breaking down and reabsorbing bone tissue (Bone destroying cells). 19  Classification of Bones Bones are classified into five categories based on their shape: specific types of markings that serve similar functions across different bones in the body: 1. Long Bones: Found in the arms and legs (e.g., femur). 2. Short Bones: Found in the wrists and ankles (e.g., Neck: The narrowing of the bone where the shaft (diaphysis) carpals). meets the end of a long bone. It plays a crucial role in 3. Flat Bones: Found in the skull and ribs (e.g., parietal connecting the main body of the bone to the joint region (e.g., bone). Right 1st rib, left radius). 4. Irregular Bones: Bones with irregular shapes, like vertebrae and facial bones. 5. Sesamoid Bones: Small, round bones found within tendons (e.g., patella). Body: The largest and main segment of a bone, which provides structure and strength (e.g., Left scaphoid, left calcaneus, body of sternum). Epicondyle: A rounded projection located above the condyle, allowing connective tissues, such as tendons and ligaments, to attach (e.g., Left humerus, left femur). General Bone Markings Bone markings feature specific characteristics that serve various purposes: Articulations: Points where bones meet, forming joints and allowing movement. Projections: Raised areas on bones where muscles, tendons, and ligaments attach for movement and support. Holes: Openings in bones that allow nerves, blood vessels, and ligaments to pass through, facilitating connections between different parts of the body. Head: A rounded, ball-like surface on the end of a bone that forms part of a joint and fits into a socket. Facet: A smooth, flat surface where two bones meet, allowing for slight movement or gliding. Condyle: A large, rounded bump on a bone that forms part of a joint, aiding in smooth articulation with another bone. 20  Tubercle: A small, rounded projection where muscles and tendons connect to the bone (e.g., C03 vertebra, mandible, left 5th rib). Crest: A raised ridge along the edge of a bone, often serving as an attachment point for connective tissues (e.g., Left ilium, left pubis, frontal bone). Foramen: A round hole in the bone that permits the passage of blood vessels, nerves, or ligaments (e.g., Right zygomatic bone, sphenoid, occipital). Spine (Spinous Process): A sharp, pronounced elevation of bone that acts as an attachment point for muscles and connective tissues (e.g., T01 vertebra, L03 vertebra, right scapula). Meatus: A tube-like channel within the bone that protects and allows for the passage of nerves and blood vessels (e.g., Right temporal bone). Tuberosity: A large or moderate projection on a bone, providing attachment areas for connective tissues such as tendons (e.g., Left femur for large projections, right 5th metatarsal for moderate). 21 Fissure: A slit or crack in the bone that typically houses blood vessels and nerves (e.g., Right maxilla). Sinus: A cavity within a bone or tissue that can function in reducing bone weight or enhancing resonance in the voice (e.g., Ethmoid bone). Sulcus: A groove in the bone surface that accommodates a nerve, blood vessel, or tendon (e.g., Right talus). BONE FRACTURES AND REPAIR A fracture is a break in the bone. Types of fractures include: 1. Closed (Simple) Fracture: The bone does not penetrate the skin. 2. Open (Compound) Fracture: The bone breaks through the skin. Common types of fractures: Comminuted Fracture: The bone is shattered into three or more pieces, often due to severe trauma. Common in older people with brittle bones. Fossa: A shallow depression on a bone’s surface that allows Compression Fracture: The bone is crushed, typically other bones to articulate or fit (e.g., Left humerus). occurring in vertebrae due to osteoporosis or high-impact injuries. Depressed Fracture: Bone is pressed inward, common in skull fractures. Impacted Fracture: The ends of the broken bone are driven into each other, often resulting from falls or direct impact. Spiral Fracture: A fracture that twists around the bone, often caused by a rotating force, like in sports injuries. Greenstick Fracture: The bone bends and cracks without breaking completely, common in children whose bones are still soft and flexible. 22 Fracture repair occurs in four stages: 1. Hematoma Formation: A blood clot forms around the fracture. 2. Fibrocartilage Callus Formation: A soft callus made of cartilage forms. 3. Bony Callus Formation: The soft callus is replaced by hard bone. 4. Bone Remodeling: The bone is reshaped to resemble its original form. SKELETAL SYSTEM DIVISIONS The human skeleton is divided into two main parts: 1. Axial Skeleton: Includes the skull, vertebral column, and thoracic cage. 2. Appendicular Skeleton: Includes the limbs and girdles. The Skull The skull is divided into two parts: the cranium and the facial bones. Cranium: Composed of 8 bones, including the frontal, parietal, temporal, and occipital bones. ○ The sphenoid and ethmoid bones are part of the cranium but not part of the skull cap. Facial Bones: Consist of 14 bones, including the mandible (jawbone) and maxillae (upper jawbone). ○ The mandible is the only movable bone in the skull. Vertebral Column The vertebral column consists of 26 vertebrae separated by intervertebral discs. It includes: 23  Cervical Vertebrae: The top 7 vertebrae. transverse) Thoracic Vertebrae: The 12 middle vertebrae. The protrusion that can be felt at the back of the neck is Lumbar Vertebrae: The 5 lower vertebrae. the non-bifid spinous process of C07 Sacrum: Made up of 5 fused vertebrae. Coccyx: Also known as the tailbone. Atlanto-Occipital Joint The atlanto-occipital joint connects the atlas to the occipital The first cervical vertebra is called the atlas, and the second is bone. It flexes the neck, allowing you to nod your head called the axis. These allow for the nodding and rotation of the head. The atlantoaxial joint connects the axis to the atlas. It permits rotational movement of the head The Thoracic Cage APPENDICULAR SKELETON The bony thorax includes the sternum (breastbone) and the Includes 126 bones that make up the limbs and girdles, including ribs. The rib cage has 12 pairs which consists of: the pectoral and pelvic girdles. These bones allow for a wide range of motion and serve as attachment points for muscles, True Ribs: The first 7 pairs, directly attached to the contributing to limb mobility. sternum. False Ribs: The last 5 pairs, which are not directly attached to the sternum. The Fetal Skull and Fontanelles A newborn's skull has fontanelles, which are soft, fibrous membranes between bones. These allow for brain growth and generally close by 24 months. Middle Ear Bones The middle ear contains three small bones, known as ossicles, that transmit sound vibrations: 1. Malleus (hammer) 2. Incus (anvil) 3. Stapes (stirrup) Atlas and Axis BONES OF THE SHOULDER GIRDLE Composed of two bones the Clavicle and Scapula Clavicle (Collarbone): The clavicle is a slender bone that connects the arm to the body. Acts as a brace to keep the arm away from the thorax and helps prevent shoulder dislocation. The collarbone is often fractured by falling on an The atlas and axis are part of the seven cervical vertebrae. outstretched arm, especially in children. These vertebrae have a few unique features: Scapula (Shoulder Blade): The scapula, often referred to as They are the smallest of the vertebrae. the "wing bone," C01—C06 have three foramina: (one vertebral and two 24  flat bone that allows for free movement of the upper Forearm (Ulna and Radius): The forearm contains two bones, limb. the ulna and radius. It has three borders (superior, medial, lateral) and is connected to the clavicle at the acromioclavicular joint. The ulna is the longer bone and is located on the side The glenoid cavity of the scapula forms a shallow of the little finger. socket for the humerus, providing limited stability but The radius, on the thumb side, allows for rotation of allowing greater flexibility in shoulder movement. the wrist and forearm. Both bones are connected by the interosseous 2 processes of the scapula membrane, and together they support forearm and Acromion Process hand movement. Enlarged lateral end of the spine. Coracoid Process "Beaklike" Points laterally over the top of the shoulder. Anchors some muscles of the arms. BONES OF THE UPPER LIMB Humerus: The humerus is the long bone of the upper arm. Its head fits into the glenoid cavity of the scapula, allowing for rotation. The humerus has greater and lesser tubercles for muscle attachment and a surgical neck that is a common site for fractures. Hand: The hand consists of carpals (wrist bones), metacarpals The deltoid muscle attaches to the deltoid (palm bones), and phalanges (finger bones). There are 8 carpal tuberosity, providing strength for arm movement. bones, 5 metacarpals, and 14 phalanges in each hand. The thumb has only two phalanges, while the other fingers have three. These bones provide a high degree of flexibility and dexterity. 25  BONES OF THE PELVIC GIRDLE Gender Difference of Pelvis Pelvic Girdle: The pelvic girdle is composed of two coxal (hip) bones that are fused from three bones: the ilium, ischium, and pubis. Illium Connect posteriorly with the sacrum. Large flaring bone that forms most of the hip bone "Alae" - wing like portion of ilium Sacroiliac joint - the one that joints the ilium and part of the sacrum Ischium Female inlet is larger and more circular Ischial tuberosity - receives body weight when in a sitting position Female pelvis is shallower Ischial spine - superior to the tuberosity. Bone are lighter and thinner Narrows the outlet of the pelvis Female ilia flare more laterally Female sacrum is shorter and Pubis less curved The most anterior and inferior part. Female ischial spine are shorter and farther apart (bigger Forms in the fusion of Rami of the pubis outlet) Obturator foramen - opening that allows blood vessels and nerves to pass into the anterior part of the thigh. Female pubic arch is more rounded. Pubic symphysis - pubic bones of each hip articulate anterior to form a cartilaginous joint. BONES OF THE LOWER LIMB During birth, the baby passes through the pelvic brim. Femur (Thigh Bone): The femur is the longest and strongest bone in the human body. Its head fits into the acetabulum of PELVIS the pelvis, and its distal end articulates with the tibia at the knee Acetabulum - Deep socket formed by the fusion of Ilium, joint. The patella, or kneecap, is a triangular bone that ischium and pubis ○ Accommodates the head of the femur. protects the knee joint and aids in leg movement. False Pelvis - Superior to the true pelvis ○ The area medial to the flaring portions of the ilia. True Pelvis - Surrounded by bone ○ Lies inferior to the flaring parts of the ilia and the pelvic brim. Outlet - The inferior opening of the pelvis measured between the ischial spines. Inlet - Superior opening between the right and left sides of the pelvic brim. Leg (Tibia and Fibula): The tibia, or shinbone, is the larger bone of the lower leg, while the fibula is thinner and located laterally. The tibia bears most of the body’s weight, while the fibula supports the tibia and forms the outer part of the ankle. The medial and lateral malleoli are bony prominences on the ankle. 26  are connected. Synovial joints, which are found in the limbs, are the most common and allow for a wide range of motion. Synovial Joints Hinge joints (e.g., elbow, knee) allow movement in one direction. Ball-and-socket joints (e.g., shoulder, hip) provide the greatest range of movement. Pivot joints (e.g., neck, forearm) allow for rotational movement. Saddle joints (e.g., thumb) offer a wide range of motion. Gliding joints (e.g., wrist, ankle) allow for limited sliding movements. Condyloid joints (e.g., knuckles) permit movement but not rotation. MUSCULAR SYSTEM FUNCTIONS OF THE MUSCULAR SYSTEM Producing Movement – Skeletal muscles contract to create movement, respond to external stimuli, and express emotions (smiling, frowning). Maintaining Posture – Muscles continuously adjust to maintain posture. Stabilizing Joints – Muscles pull on bones and stabilize joints Foot: The foot includes tarsal bones (ankle), metatarsals through tendons. (instep), and phalanges (toes). The calcaneus, or heel bone, is the largest tarsal bone and bears much of the body’s weight. The Generating Heat – Muscle activity (ATP use) produces heat, talus is the second-largest tarsal bone, located above the maintaining body temperature. calcaneus. The foot's structure allows for balance and movement. Muscles are excitable, contractible (shorten), extensible (stretch), and elastic (return to original shape). TYPES OF MUSCULAR TISSUE Skeletal Muscle – Large, multinucleate, cigar-shaped fibers. Smooth Muscle – Spindle-shaped cells; slow, sustained contractions. Cardiac Muscle – Organized in spiral bundles; steady contraction rate (regulated by pacemaker). JOINTS Joints are classified based on their function and structure. Synarthroses are immovable joints, amphiarthroses are slightly movable, and diarthroses are freely movable. Joints can also be fibrous, cartilaginous, or synovial, depending on how the bones 27  CONNECTIVE TISSUE COVERING ENERGY FOR CONTRACTION Fascia – Surrounds muscles, separating them from Muscle contraction is powered by ATP, replenished by others. cellular respiration, glycolysis, and creatine phosphate. Tendon – Connects muscle to bone. Aponeurosis – Flat, broad tendon connecting muscles. HEAT PRODUCTION Muscle contractions generate heat to maintain body MUSCLE TISSUE ORGANIZATION temperature, as 60% of the energy from glucose is lost as heat. Endomysium – Surrounds individual fibers. Perimysium – Surrounds fascicles (bundles of fibers). LEVER SYSTEMS Epimysium – Surrounds the entire muscle. Muscles act on bones as levers at joints (fulcrums). SKELETAL MUSCLE STRUCTURE Muscle fibers are composed of myofibrils (containing thick and 1. First-Class – Fulcrum between effort and load (e.g., thin filaments). raising the head). 2. Second-Class – Load between fulcrum and effort (e.g., Sarcolemma – Cell membrane; sarcoplasm – Cytoplasm. standing on tiptoe). 3. Third-Class – Effort between fulcrum and load (e.g., Sarcomere – Functional unit; alternating light and dark bands flexing the forearm). due to filament arrangement. MUSCLE ATTACHMENT Myofilament Structure Origin – Immovable attachment point. Thick Filaments – Myosin, powered by ATPase. Insertion – Movable attachment point during contraction. Thin Filaments – Actin with binding sites for myosin. BASIC BODY MOVEMENTS Troponin-Tropomyosin Complex – Regulates binding in 1. Flexion: Decreasing the angle between two bones, muscle contraction. typically bending a joint. Example: Bending the elbow or knee. MUSCLE CONTRACTION PROCESS Neuromuscular Junction – Motor neurons release 2. Extension: Increasing the angle between two bones, acetylcholine (ACh), triggering muscle contraction. typically straightening a joint. Example: Straightening the leg or arm. Sliding Filament Theory – Thin filaments slide past thick ones, shortening sarcomeres and causing contraction. 3. Abduction: Moving a limb away from the midline of the body. Example: Raising the arms or legs sideways. Power Stroke – Myosin binds to actin, pulling filaments inward, 4. Adduction: Moving a limb toward the midline of the fueled by ATP hydrolysis. body. Example: Bringing the arms or legs back down to Relaxation – ACh is broken down by acetylcholinesterase; the sides. calcium is reabsorbed, allowing muscle relaxation. 5. Rotation: Turning a bone around its own axis. Example: Turning the head side to side. 6. Circumduction: Moving a limb in a circular motion, combining flexion, extension, abduction, and adduction. Example: Swinging the arm in a circle. 7. Inversion: Turning the sole of the foot inward. 8. Eversion: Turning the sole of the foot outward. 9. Dorsiflexion: Raising the toes toward the shin. 10. Plantar Flexion: Pointing the toes downward. 11. Supination: Rotating the forearm so the palm faces upward or forward. 12. Pronation: Rotating the forearm so the palm faces downward or backward. 28  INTERACTION OF SKELETAL MUSCLES Prime Movers: Muscles primarily responsible for producing a specific movement. Example: Biceps brachii during arm flexion. FACIAL MUSCLES Antagonists: Muscles that oppose or reverse a movement. 1. Frontalis Example: Triceps during arm flexion. ○ Origin: Epicranial aponeurosis ○ Insertion: Skin of eyebrows Synergists: Assist prime movers by adding force or stabilizing ○ Action: Raises eyebrows, wrinkles forehead joints. Example: Brachialis assists in elbow flexion. 2. Corrugator ○ Origin: Superciliary arch Fixators: Specialized synergists that stabilize the origin of a ○ Insertion: Skin above the middle of the prime mover, preventing unnecessary movement. Example: forehead Muscles of the back stabilize the scapula during arm ○ Action: Draws eyebrows downward and movements. medially (frowning) 3. Procerus NAMING OF SKELETAL MUSCLES ○ Origin: Nasal bone Direction of Muscle Fibers: Refers to orientation relative to an ○ Insertion: Skin of forehead imaginary line, such as the midline. ○ Action: Wrinkles nose, draws eyebrows down 4. Depressor Supercilii Rectus (straight), e.g., rectu