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Villi: Structure and Fun!(ction) By: Guinea McGinnis, Reese’s Reser, Pikachu Bui, Tiny Garcia How it works The lining of the small intestine is characterized by numerous circular folds called “plicae circulares.” The plicae are lined with fingerlike villi. From a cross-sectional view, the villus contains a network of capillaries which surround a specialized lymphatic vessel known as a lacteal. The epithelium of an intestinal villus consists of columnar cells which are covered with microvilli. This succession of folds and projections increases the surface of the intestinal lining for efficient absorption. Carbohydrates are absorbed by the villi and then enter the capillary. Fat molecules are digested and absorbed into the epithelial cells of the villus. The fats are formed into clusters called chylomicrons which pass into the lacteal. Lymph carries chylomicrons away from the villus. Proteins are broken down first into peptides, then into amino acids. These are absorbed into the villi, then into the capillary. What it looks like Magic School Bus http://www.youtube.com/watch?v=zJieJ3_ R2Do (3:48) Neuron Anatomy and Neural Communication Neurons Dendrites Cell Body Myelin Sheath Axon of another neuron Axon Dendrites of another neuron Neural Anatomy Dendrite the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body Axon the extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glands Neural Anatomy and communication Synapse junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron tiny gap at this junction is called the synaptic gap or cleft Synapse movie Specific Parts: The Neuron Structure Specific Parts: The Neuron Function 1. 3. 2. Neurons = 3 functions: Reception, Conduction, Transmission Action Potential When dendrites stimulated, the delicate balance is altered Membrane breaks down Positively charged ions rush in (depolarization) Charge = less negative Causes release of chemicals from terminal buttons Relay Race Action Potential starts at dendrite Through cell body Down Axon Axon Terminals • How does it get to the next cell’s dendrites? • Neurons don’t touch Synapse = millionth inch gap In synapse = vesicles w/ neurotransmitters • Chemical messengers that transmit info Communication Impulse releases neurotransmitter from vesicles Neurotransmitter enters synaptic gap Neurotransmitter binds to receptors on the receiving neuron Myelin Sheath Fatty material made by glial cells Insulates the axon Allows for rapid movement of electrical impulses along axon Nodes of Ranvier: gaps in myelin sheath where action potentials are transmitted Multiple sclerosis is a breakdown of myelin sheath Speed of neural impulse Ranges from 2 – 200+ mph Myelinization clip Myelin conduction clip Neurotransmitters chemical messengers that traverse the synaptic gaps between neurons when released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether it will generate a neural impulse Neurotransmitters (>60) Acetylcholine (ACh) st substance identified as NT 1 Links motor neurons and muscles (contract or relax) • e.g. curare vs black widow spider Also involved in memory, learning, sleep, dreaming (acetylcholine movie) Endorphins (the brain’s own morphine) 1973 injected rats with morphine Bound like NTs Brain had receptors for exogenous substance? • Brain must produce its own morphine • Released during pain and discomfort Artery White blood cells Platelets Red blood cells RBC Structure And Function Have no organelles or nuclei Hemoglobin – oxygen carrying protein Each RBC has about 280 million hemoglobin molecules Biconcave shape – 30% more surface area • Deliver O2 • Remove metabolic wastes • Maintain temperature, pH, and fluid volume • Protection from blood loss- platelets • Prevent infection- antibodies and WBC • Transport hormones Erythrocytes Erythrocytes – Red Blood Cells (RBCs) Oxygen-transporting cells Most numerous of the formed elements 7.5 µm in diameter (diameter of capillary 8 – 10µm) Females: 4.3 – 5.2 million cells/cubic millimeter Males: 5.2 – 5.8 million cells/cubic millimeter Made in the red bone marrow in long bones, cranial bones, ribs, sternum, and vertebrae Average lifespan 100 – 120 days Erythrocyte7.5m in dia Anucleate- so can't reproduce; however, repro in red bone marrow Hematopoiesis- production of RBC Function- transport respiratory gases Hemoglobin- quaternary structure, 2 chains and 2 chains Lack mitochondria. Why? 1 RBC contains 280 million hemoglobin molecules Men- 5 million cells/mm3 Women- 4.5 million cells/mm3 Life span 100-120 days and then destroyed in spleen (RBC graveyard) Blood Cell Production Leukocytes – White Blood Cells (WBCs) Protect the body from infectious microorganisms 4,800 – 11,000/cubic millimeter Function outside the bloodstream in loose connective tissue Diapedesis – circulating leukocytes leave the capillaries WBCs have a nucleus and are larger than RBCs Most produced in bone marrow Lifespan of 12 hours to several years Leukocytes – White Blood Cells (WBCs) Two types of leukocytes Granulocytes Agranulocytes Differential WBC Count Never Let Monkeys Eat Bananas Figure 17.5 White Blood Cells Type Of White Blood Cells % By Volume Of WBC Description Function Neutrophils 60 – 70 % Nucleus has many interconnected lobes; blue granules Phagocytize and destory bacteria; most numerous WBC Eosinophils 2–4% Nucleus has bilobed nuclei; red or yellow granules containing digestive enzymes Play a role in ending allergic reactions <1% Bilobed nuclei hidden by large purple granules full of chemical mediators of inflammation Function in inflammation medication; similar in function to mast cells 20 – 25 % Dense, purple staining, round nucleus; little cytoplasm the most important cells of the immune system; effective in fighting infectious organisms; act against a specific foreign molecule (antigen) 4–8% Largest leukocyte; kidney shaped nucleus Transform into macrophages; phagocytic cells Basophils Lymphocytes (B Cells and T Cells) Monocytes Granulocytes Neutrophils – most numerous WBC Phagocytize and destroy bacteria Nucleus – has two to six lobes Granules pick up acidic and basic stains Figure 17.4a Granulocytes Eosinophils – compose 1 – 4% of all WBCs Play roles in ending allergic reactions, parasitic infections Figure 17.4b Granulocytes Basophils – about 0.5% of all leukocytes Nucleus – usually two lobes Granules secrete histamines Function in inflammation mediation, similar in function to mast cells Agranulocytes Lymphocytes – compose 20 – 45% of WBCs The most important cells of the immune system Nucleus – stains dark purple Effective in fighting infectious organisms Act against a specific foreign molecule (antigen) Two main classes of lymphocyte T cells – attack foreign cells directly B cells – multiply to become plasma cells that secrete antibodies Figure 17.4d Agranulocytes Monocytes – compose 4–8% of WBCs The largest leukocytes Nucleus – kidney shaped Transform into macrophages • Phagocytic cells Figure 17.4e A rod cell (upper) and a cone cell From which direction would light come? Retina Several layers of Rods Cones cells in inner More abundant Less abundant surface of choroid Center of Periphery of Contains retina retina photorecepto Black & White Color rs - Rods & Poor definition High resolution Cones Night Vision Daytime Muscle Tissue Alternating contraction and relaxation of cells Chemical energy changed into mechanical energy 40 3 Types of Muscle Tissue Skeletal muscle attaches to bone, skin or fascia striated with light & dark bands visible with scope voluntary control of contraction & relaxation 41 3 Types of Muscle Tissue Cardiac muscle striated in appearance involuntary control autorhythmic because of built in pacemaker 42 3 Types of Muscle Tissue Smooth muscle attached to hair follicles in skin in walls of hollow organs -- blood vessels & GI nonstriated in appearance involuntary 43 Functions of Muscle Tissue Producing body movements Stabilizing body positions Regulating organ volumes bands of smooth muscle called sphincters Movement blood, lymph, urine, air, food and fluids, sperm Producing of substances within the body heat involuntary contractions of skeletal muscle (shivering) 44 Connective Tissue Components 45 Nerve and Blood Supply Each skeletal muscle is supplied by a nerve, artery and two veins. Each motor neuron supplies multiple muscle cells (neuromuscular junction) Each muscle cell is supplied by one motor neuron terminal branch and is in contact with one or two capillaries. nerve fibers & capillaries are found in the endomysium between individual cells 46 Fusion of Myoblasts into Muscle Fibers Every mature muscle cell developed from 100 myoblasts that fuse together in the fetus. (multinucleated) Mature muscle cells can not divide Muscle growth is a result of cellular enlargement & not cell division 47 Two Types of Smooth Muscle Visceral (single-unit) in the walls of hollow viscera & small BV autorhythmic gap junctions cause fibers to contract in unison Multiunit individual fibers with own motor neuron ending found in large arteries, large airways, arrector 48 Excitation - Contraction Coupling All the steps that occur from the muscle action potential reaching the T tubule to contraction of the muscle fiber. 49