Organ Systems_ Putting the Pieces Together
The Body's Framework: The Skeletal System
Multicellularity: Allows animals to achieve larger sizes compared to single-celled organisms; requires supportive systems for structural integrity and muscle attachment.
Types of Skeletons:
Hydrostatic Skeletons:
Utilize water pressure for structural support.
Muscle contractions move water, enabling body movement.
Exoskeletons:
Rigid structures located outside the body; provide muscle attachment and protection.
Endoskeletons:
Found within the body; similar functions as exoskeletons.
Focus on Vertebrate Endoskeleton:
Composed of bones, primarily bone tissue.
Bone Categorization by Density:
Spongy Bone: Open network, appears spongy, aligns with stress lines for strength.
Compact Bone: Dense, solid appearance, forms from consolidated spongy bone.
Vertebrate Endoskeleton
Divided into:
Axial Skeleton:
Comprises the skull, vertebral column, and rib cage along the body's axis.
Appendicular Skeleton:
Includes bones of limbs and girdles, facilitating locomotion in tetrapods.
Anatomical Structure Overview
Axial Skeleton Components:
Skull (Cranial and Facial portions)
Vertebral column
Thoracic cage (Sternum and Ribs)
Appendicular Skeleton Components:
Pectoral girdle (Clavicle, Scapula)
Upper limb (Humerus, Radius, Ulna)
Pelvic girdle (Hip bones)
Lower limb (Femur, Patella, Tibia, Fibula)
Muscles and Contraction
Skeletal Muscles: Critical for movement and are formed of skeletal muscle tissue, which is striated, voluntary, and multinucleated.
Functions of Skeletal Muscles:
Movement
Stability
Control of passages
Heat production
Glycemic control
Muscle Structure:
Muscles attach to bones via tendons; separated by a fascia.
Made of muscle fascicles, surrounded by connective tissue.
Muscle Fiber Structure:
Comprised of myofibrils (responsible for contraction)
Contains thick (myosin) and thin (actin, with troponin and tropomyosin) filaments.
Sarcomere: Functional contraction unit.
The Sliding Filament Theory
Muscle Contraction Process:
Calcium ions are released from the sarcoplasmic reticulum.
Calcium binds to troponin, moving tropomyosin away from actin.
Myosin binds with actin, forming a cross-bridge, and undergoes ATP-driven contraction.
The Digestive System
Nutrient Acquisition: Animals must consume materials (heterotrophic).
Digestive Mechanisms:
Intracellular Digestion:
Occurs within cells (e.g., amoebae, sponges).
Extracellular Digestion:
Involves enzymes released into the digestive tract (most animals).
Types of Digestive Tracts:
Incomplete Digestive Tracts: One opening (e.g., jellyfish).
Complete Digestive Tracts: Two openings—mouth and anus (e.g., humans).
Digestive Process Overview
Pathway: Mouth > Pharynx > Esophagus > Stomach > Small Intestine > Large Intestine > Rectum > Anus.
Digestive Steps:
Chewing forms bolus, followed by peristalsis.
Stomach churns food, secreting gastric juices (pepsinogen + HCl = pepsin).
Chyme enters small intestine for nutrient absorption, facilitated by accessory organs (salivary glands, liver, gall bladder, pancreas).
Accessory Organs in Digestion
Liver: Produces bile (lipid digestion).
Pancreas: Produces enzymes (trypsin, amylase, lipase, nucleases) for nutrient breakdown.
Chyme Movement: Water and salts absorbed in the large intestine, leading to feces formation.
The Respiratory System
Oxygen Requirement: Necessary for cellular respiration (ATP production).
Respiratory Mechanisms: Include simple diffusion, cutaneous exchange, gills, tracheae, and lungs.
Human Respiratory System Division: Upper and Lower Tract.
Pathway of Air in the Respiratory System
Nose (cleans air)
Pharynx (directs airflow)
Larynx (vocal cords and epiglottis)
Trachea (branches into bronchi)
Bronchi to Bronchioles to Alveoli (gas exchange)
Breathing and Gas Exchange
Breathing Mechanics:
Diaphragm and intercostal muscles cause lung expansion for air intake and compress for exhalation.
The Circulatory System
Function: Transports nutrients and gases throughout the body.
Circulatory Types: Open (e.g., invertebrates) vs. Closed (e.g., vertebrates).
Components of the Cardiovascular System
Blood: Contains formed elements (erythrocytes, leukocytes, platelets) and plasma.
Blood Vessels: Arteries (away from heart), veins (toward heart), and capillaries (exchange sites).
Heart Structure: Four chambers (left atrium/ventricle and right atrium/ventricle); contains valves to prevent backflow.
Blood Circulation Pathways
Pulmonary Circuit: Carries deoxygenated blood to lungs for gas exchange; returns oxygenated blood to heart.
Systemic Circuit: Oxygenated blood distributes to the body; deoxygenated blood returns to heart.
Cardiac Cycle: Blood flow from heart and back, ensuring proper circulation.
The Excretory System
Function: Removes metabolic wastes (e.g., carbon dioxide, nitrogenous wastes).
Human Excretion: Primarily urea via the urinary system.
Components of Human Excretory System
Organs: Kidneys (urine production), Ureters (transport), Bladder (storage), Urethra (expulsion).
Nephrons: Perform filtration, reabsorption, and secretion in urine formation.
Reproductive Strategies
Reproduction Types: Asexual (fast, clones) vs. Sexual (gamete fusion, genetic diversity).
Asexual Methods: Budding, fragmentation, fission.
Sexual Fertilization: Can be external (environment) or internal (within female).
Male Reproductive System Structure
Testes: Produce sperm; located in the scrotum (temperature regulation).
Accessory Glands: Produce fluid (semen) for sperm transport.
Penis: Conduit for semen and urine.
Female Reproductive System Structure
Ovaries: Produce eggs and hormones.
Uterine Tubes: Carry eggs to uterus; site for fertilization.
Uterus and Vagina: Involved in embryo implantation and birth.
The Nervous System
Coordination: Maintains body systems for homeostasis through neuronal communication.
Neurons: Transmit electrical signals; junctions convert signals to chemical neurotransmitters.
Nervous System Divisions
Central Nervous System: Brain and spinal cord—information processing.
Peripheral Nervous System: Nerves linking CNS with body organs; divides into sensory (detects stimuli) and motor (initiates response).
Reflex Arc Mechanism
Pathway: Sensory neurons detect stimulus ➔ Afferent nerves to CNS ➔ Interneurons process ➔ Efferent nerves to effectors (muscles).
Sensory Receptor Types
Chemoreceptors: Detect chemicals.
Photoreceptors: Detect light.
Mechanoreceptors: Sense pressure.
Thermoreceptors: Sense temperature.
Nociceptors: Detect pain.
The Body's Framework: The Skeletal System
Multicellularity: Supports larger animal sizes requiring structural integrity.
Types of Skeletons:
Hydrostatic Skeletons: Use water pressure for support and motion.
Exoskeletons: External rigid structures for muscle attachment/protection.
Endoskeletons: Internal structures with similar functions.
Vertebrate Endoskeleton:
Bone Types:
Spongy Bone: Open, lightweight, aligns with stress.
Compact Bone: Dense and solid.
Skeleton Division:
Axial Skeleton: Skull, vertebral column, rib cage.
Appendicular Skeleton: Limb bones and girdles.
Muscles and Movements:
Skeletal Muscles: Striated, voluntary, responsible for movement, stability, and heat.
Muscle Structure: Comprised of muscle fibers, myofibrils, and sarcomeres (functional unit).
Contraction Mechanism: Calcium ions release, enabling myosin-actin interaction through the Sliding Filament Theory.
Digestive System:
Digestion Types: Intracellular and extracellular; includes complete and incomplete tracts.
Pathway: Mouth > Pharynx > Esophagus > Stomach > Small Intestine > Large Intestine > Anus.
Accessory Organs: Liver, pancreas aid digestion.
Respiratory System:
Mechanisms: Include various structures for gas exchange (e.g., lungs, gills).
Breathing Mechanics: Involves diaphragm and intercostal muscles.
Circulatory System:
Function: Transports nutrients and gases; divided into open and closed systems.
Components: Blood, blood vessels, heart structure; includes pulmonary and systemic circuits.
Excretory System:
Function: Removes waste; human excretion via kidneys.
Components: Kidneys, ureters, bladder, urethra.
Reproductive Strategies:
Types: Asexual (fast, clones) vs. Sexual (genetic diversity); internal or external fertilization.
Nervous System:
Function: Coordinates body systems via neuronal communication.
Divisions: Central (brain and spinal cord) and peripheral (nerves); processes through reflex arcs.