Bi Sc 004- Weeks 4,5,6 Notes
Bi Sc 004- Weeks 4,5,6 Notes BI SC 004
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BI SC 004
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This 13 page Bundle was uploaded by Jordan Notetaker on Sunday February 21, 2016. The Bundle belongs to BI SC 004 at Pennsylvania State University taught by Jennifer Intelicato-Young in Spring 2016. Since its upload, it has received 38 views. For similar materials see Human Body: Form and Function in Biological Sciences at Pennsylvania State University.
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Date Created: 02/21/16
Skeletal System Notes - The skeletal system consists of two types of connective tissue: bone and the cartilage found at joints. In addition, ligaments, formed of fibrous connective tissue, join the bones. - The skeleton: Support. The bones of the legs support the entire body when we are standing, and the bones of the pelvic girdle support the abdominal cavity. Movement. The skeletal system works with the muscular system to provide movement. Protection. The bones of the skull protect the brain; the rib cage protects the heart and lungs; and the vertebrae protects the spinal cord, which makes nervous connections to all the muscles of the limbs. Production of blood cells. All bones in the fetus have red bone marrow that produces blood cells. In the adult, only certain bones produce blood cells. Storage of minerals and fat. All bones have a matrix that contains calcium phosphate, a source of calcium ions and phosphate ions in the blood. Fat is stored in yellow bone marrow. - The shaft, or main portion of the bone, is called the diaphysis. It has a large medullary cavity whose walls are composed of compact bone. This cavity is lined with a thin, vascular membrane (the endosteum) and is filled with yellow bone marrow, which stores fat. The expanded region at the end of a long bone is called an epiphysis (pl., epiphyses). These are separated from the diaphysis by a small region of mature bone called the metaphysis, which contain the epiphyseal plate, a region of cartilage that allows for bone growth. They are composed largely of spongy bone that contains red bone marrow, where blood cells are made, coated with a thin layer of hyaline cartilage (or articular cartilage), because it occurs at a joint. Except for the articular cartilage on the bones end, a long bone is completely covered by a layer of fibrous connective tissue called the periosteum. This covering contains blood vessels, lymphatic vessels, and nerves. - Compact bone is highly organized and composed of tubular units called osteons. In a cross section of an osteon, bone cells called osteocytes lie in lacunae (sing., lacuna), tiny chambers arranged in concentric circles around a central canal. Matrix fills the space between the rows of lacunae. Tiny canals called canaliculi (sing., canaliculus) run through the matrix. These connect the lacunae with one another and with the central canal. The cells stay in contact by strands of cytoplasm that extend into the canaliculi. Osteocytes nearest the center of an osteon exchange nutrients and wastes with the blood vessels in the central canal. These cells then pass on nutrients and collect wastes from the other cells via gap junctions. Compared with compact bone, spongy bone has an unorganized appearance. It contains numerous thin pates, called trabeculae, separated by unequal spaces. Although this makes spongy bone lighter, it is still designed for strength. Just as braces are used for support in building, the trabeculae follow lines of stress. The spaces of spongy bone are often filled with red bone marrow, a specialized tissue that produces all types of blood cells. - Cartilage is not as strong as bone, but it is more flexible. Its matrix is gel-like and contains many collagenous and elastic fibers. The cells, called chondrocytes, lie within lacunae that are irregularly grouped. Has no nerves or blood vessels; relies on neighboring tissue for nutrient and waste exchanging, making it slow to heal. Three types of cartilage: hyaline is firm and somewhat flexible; the matrix appears uniform and glassy, but contains a generous supply of collagen fibers; found at the ends of long bones, in the nose, at the ends of ribs, larynx and the trachea. Fibrocartilage is stronger than hyaline b/c the matrix contains wide rows of thick, collagenous fibers; able to withstand both tension and pressure and is found where support is of prime importance – in the disks between the vertebrae and knee cartilage. Elastic cartilage is more flexible than hyaline, b/c the matrix contains mostly elastin fibers; found in ear flaps and epiglottis. - Fibrous connective tissue contains rows of cells called fibroblasts separated by bundles of collagenous fibers. This tissue makes up ligaments and tendons. Ligaments connect bone to bone. Tendons connect muscle to bone at a joint (articulation). - The axial skeleton lies in the midline of the body and consists of the skull, hyoid bone, vertebral column, and the rib cage. The skull is formed by the cranium (braincase) and the facial bones. However, some cranial bones contribute to the face. The cranium protects the brain; in adults it is composed of 8 bones fitted together tightly; in newborns, certain cranial bones are not completely formed. Instead, these bones are joined by membranous regions called fontanels, which usually close by the age of 16 months by the process of intramembranous ossification. The major bones of the cranium have the same names as the lobes of the brain: frontal, parietal, occipital, and temporal. On the top of the cranium, the frontal bone forms the forehead, the parietal bones extend to the sides, and the occipital bone curves to form the base of the skull. Here there is a large opening, the foramen magnum, through which the spinal cord passes and becomes the brain stem. Below the much larger parietal bones, each temporal bone has an opening (external auditory canal) that leads to the middle ear. The sphenoid bone, shape like a bat with outstretched wings, extends across the floor of the cranium from one side to the other; keystone of the cranial bones, b/c all the other bones articulate with it; completes the sides of the skull and contributes to forming the eye sockets. The ethmoid bone, which lies in front of the sphenoid, also helps form the sockets and the nasal septum. Some of the bones of the cranium contain the sinuses, air spaces lined by mucous membrane. The most prominent of the facial bones are the mandible (lower jaw), the maxillae (sing., maxilla), the zygomatic bones and the nasal bones. - The vertebral column consists of 33 vertebrae. Normally the column has four curvatures that provide more resilience and strength for an upright posture than a straight column could provide. Scoliosis is an abnormal lateral (sideways) curvature of the spine. Kyphosis is an abnormal posterior curvature that results in hunchback. An abnormal anterior curvature results in lordosis or swayback. - The appendicular skeleton consists of the bones within the pectoral and pelvic girdles and their attached limbs. A pectoral (shoulder) girdle and upper limb are specialized for flexibility. The pelvic (hip) girdle and lower limbs are specialized for strength. - The body has left and right pectoral girdles. Each consists of a scapula (shoulder blade) and a clavicle (collarbone). The clavicle extends across the top of the thorax; joins with the sternum and the acromion process of the scapula, a visible bone in the back. The muscles of the arm and chest attach to the coracoid process of the scapula. The glenoid cavity of the scapula joins with and is much smaller than the head of the humerus. Tendons that extend to the humerus from 4 small muscles originating on the scapula form the rotator cuf. The components of a pectoral girdle freely follow the movements of the upper limb, which consists of the humerus in the arm and the radius and ulna in the forearm. The humerus, the single long bone in the arm, has a smoothly rounded head that fits into the glenoid cavity of the scapula. The shaft of the humerus has a tuberosity where the deltoid, a shoulder muscle, attaches. - The pelvic girdle (hip girdle) consists of 2 heavy, large coxal bone (hip bones). The pelvis is a basin composed of the pelvic girdle, sacrum, and coccyx; bears the weight of the body, protects the organs within the pelvic cavity, and serves as the place for attachment for the legs. The femur (thighbone) is the longest and strongest bone in the body. The head of the femur articulates with the coxal bones at the acetabulum, and the short neck better positions the legs for walking. The femur has two large processes, the greater and lesser trochanters, which are places of attachment for thigh muscles, butt muscles, and hip flexors. At its distal end, the femur has medial and lateral condyles that articulate w/ the tibia of the leg. This is the region of the knee and the patella (kneecap). The patella is held in place by the quadriceps tendon, which continues as a ligament that attaches to the tibial tuberosity. At the distal end, the medial malleolus of the tibia causes the inner bulge of the ankle. The fibula is the more slender bone in the leg. Articulations - Bones are joined at the joints, classifies as fibrous, cartilaginous, or synovial. Many fibrous joints, such as the sutures between the cranial bones are immovable. Cartilaginous joints may be connected by hyaline cartilage, as in the costal cartilages that join the ribs to the sternum. Other cartilaginous joints are formed by fibrocartilage, as in the intervertebral disks. Cartilaginous joints tend to be slightly movable. Synovial joints are freely movable. - Osteoblasts are bone-forming cells. They secrete the organic matrix of bone and promote the deposition of calcium salts into the matrix - Osteocytes are mature bone cells derived from osteoblasts. They maintain the structure of bone. - Osteoclasts are bone-absorbing cells. They break down bone and assist in returning calcium and phosphate to the blood. - The term ossification refers to the formation of bone. In intramembranous ossification, bones develop between sheets of fibrous connective tissue. In endochondral ossification, most of the bones of the human skeleton are formed within the cartilage; during this, bone replaces the cartilaginous models of the bones. - When the epiphyseal plates close, bone lengthening can no longer occur; in women this happens at about ages 16-18 and in men it doesn’t happen until age 20. Portions of other types of bones may continue to grow until age 25. Hormones, chemical messengers that are produced by one part of the body and act on a diferent part of the body, are secreted by the endocrine glands and distributed about the body by the bloodstream. Hormones control the activity of the epiphyseal plate. - Bone is constantly being broken down by osteoclasts and reformed by osteoblasts in the adult. As much as 18% of bone is recycled each year. This process is often call bone remodeling, normally keeps bones strong. In Paget disease, new bone is generated at a faster-than-normal- rate. This produces bone that’s softer and weaker than normal bone and can cause bone pain, deformities and fractures. - Repair of a bone is required after it breaks/fractures. Fracture repair takes place over a span of several months in a series of four steps: Hematoma. After a fracture, blood escapes from ruptured blood vessels and forms a hematoma (mass of clotted blood) in the space between the broken bones; forms within 6-8 hours. Fibrocartilaginous callus. Tissue repair begins and a fibrocartilaginous callus fills the space between the ends of the broken bone for about 3 weeks. Bony callus. Osteoblasts produce trabeculae of spongy bone and convert the fibrocartilage callus to a bony callus that joins the broken bones together. The bony callus lasts about 3-4 months. Remodeling. Osteoblasts build new compact bone at the periphery. Osteoclasts absorb the spongy bone, creating a new medullary cavity. Muscles III: Muscle tissue can only continue contracting if it has enough ATP to power the process. Muscle contraction is an energy dependent process. This ATP is generated by three different biochemical pathways. Glycolysis is a process where a single molecule of Glucose is broken down into two molecules of Pyruvate. This process occurs with or without Oxygen (O2) being present. The cell gains a pair of ATP for use in contraction. The cell then has the problem of figuring out what to do w/ the 2 pyruvate molecules. They must be converted into something else or they will essentially build up to toxic levels. Aerobic respiration takes place in mitochondria if O2 is present. A series of chemical reactions converts each Pyruvate into CO2 and water. The CO2 is then removed from the body by the lungs and excess water is removed by the kidneys. As this process goes on a total of 36 more ATP are generated. Below shows sugar being broken down into energy. C H6O12G6ucose) + 6O 6CO2+ 6H O2+ ENER2Y Anaerobic fermentation takes place if all of the oxygen available to the muscle cell is used up. Using this process, no ATP energy is produced, and actually, the cell will produce the waste product lactic acid. So, if oxygen is readily available, the cell can do Glycolysis and Aerobic Respiration and get 38 ATP to use for muscle contraction. If the cell has used up all of the oxygen it can still do Glycolysis and get a pair of ATP, but it will be forced to do fermentation for no energy bonus and will end up making organic acids. Since the cell still needs the ATP for contraction the only way to make up for this lack of ATP is to break down enough glucose to make a total of 36 more ATP. Oxygen makes the whole process 18 times more efficient so there are mechanisms used to make sure cells don’t run out of oxygen easily. Muscle Fatigue - Lack of ATP Muscles get tired when they exercise for a variety of reasons. The main one is that they run out of ATP and can no longer contract. All facets of muscle contraction require ATP from the action potential to the myosin pulling on the actin to the stopping of the contraction. Without a carbohydrate source no ATP can be generated. Having oxygen on hand can dramatically slow the rate at which sugars are used up. Without oxygen the cells needs 18 times the amount of carbohydrate to generate the same number of ATP when oxygen is used. That means that once the cell runs out of oxygen, it will start using the remaining sugars almost 20 times faster than before so the muscle gets tired out faster. Another complication happens when the oxygen is used up and lactic acid begins to accumulate in the cell. The lactic acid drops the pH which interferes with protein function, including the working of the thin and thick filaments. A last and rarer complication can happen when a muscle is stimulated very fast for a relatively long period of time. Junctional fatigue occurs when the motor neurons use up all of the Acetylcholine at the axon terminus. There is only a limited supply on hand in the motor neuron. A motor neuron can make more but it can take some time. If there is no Acetylcholine then the cells cannot be stimulated to contract. Causes of muscle cramps include: ATP depletion, dehydration, ion imbalances. Most muscle cramps will eventually pass with time but the situation can be improved by massage or stretching. Both of these things will increase circulation to the afected area and restore the proper balance. Skeletal Muscles: General Characteristics Skeletal muscle is under voluntary control, meaning that a person can cause a muscle to contract or keep it relaxed. Once the decision is made to cause a contraction, the brain then generates the appropriate signals that are sent out to the proper muscle to cause the desired body movement. Skeletal muscles also have a sarcomere arrangement of the Myofilaments and have transverse tubules. They do not contain gap junctions like Cardiac muscle but the contractions tend to be fast. Types of skeletal muscle fibers are based on the rate of ATP usage of the cells & the methods of ATP production of the cells. Some refer to these groups as Fast Twitch and Slow Twitch fibers. Fast twitch fibers give strong contractions but get tired easily, while slow twitch fibers are not as strong but can contract for far longer before becoming fatigued. These fibers can also be called Red and White fibers. The color relates to the amount of a protein called Myoglobin that these cells contain. Myoglobin is a protein much like Hemoglobin that allows the cells to store oxygen and allows for more efficient ATP production, thus preventing fatigue. Red fibers contain lots of myoglobin, can store lots of oxygen and therefore can contract for longer periods of time. White fibers do not have as much myoglobin and oxygen so they fatigue much easier. 1. Slow Oxidative Fibers These muscle cells are the smallest and tend to be very fatigue resistant. They contract for a long time before tiring because they generate ATP using the Aerobic respiration pathway. This is possible because they're red fibers which contain lots of myoglobin and oxygen. They also have lots of mitochondria and can produce an enormous amount of ATP with small amounts of carbohydrate. This efficiency comes at a price, the contractions are not very strong and tend to be a little slower than others. The Aerobic respiration pathway is very efficient but it's also slow at producing lots of ATP. 2. Fast Oxidative Fibers These muscle cells are somewhat fatigue resistant. They also have lots of myoglobin and oxygen and generate ATP using the Aerobic respiration pathway. They have many mitochondria as well. These cells have faster contractions and tend to fatigue a bit easier than the slow oxidative cells. 3. Fast Glycolytic Fibers These cells are by far physically the largest fibers of all three types. They are considered white fibers which means they do not contain much myoglobin or store much oxygen on hand and thus will quickly run out of the ability to produce ATP. This will cause the cells to fatigue easily. They produce the bulk of the ATP anaerobically which means they cannot be as efficient at using the carbohydrates that are available. To compensate for using so much sugar to get a needed level of ATP production, these cells will store extra carbohydrates inside them in the form of glycogen. This helps the cells contract for a little longer but still the cell will fatigue much sooner than all other types. However, the cells will produce their ATP very rapidly allowing for a very fast, strong contraction. Muscle Training Any given muscle will have a combination of all three muscle cell types. A leg muscle will contain many individual cells organized into motor units. Each motor unit will only contain one type of muscle cell however. One motor unit will be all slow oxidative cells another motor unit will be all fast glycolytic cells. The brain gauges the amount of force needed to compete a task and then stimulates certain motor units as needed. The motor units stimulated by jogging are diferent than those stimulated by sprinting up some stairs. The more force required, the more motor units stimulated. Sports & Exercise Hypertrophy is an increase in fiber diameter based on exercise. The acronym for RICE therapy stands for Rest the injured muscle, Ice, Compression, and Elevation. Cardiac Muscles have the following features: They are under involuntary control which means one cannot consciously make the heart beat faster or stop. Their cells have sarcomere structures just like skeletal muscle. Cardiac cells, however, have gap junctions which allows all the cells to coordinate contractions. They also have many anchoring junctions to hold the heart together as it stretches and contracts. The cells have more and larger mitochondria than other muscle cells types because cardiac muscle is continuously contracting. There are two muscle fiber networks for the upper and lower chambers of the heart. The two groups of muscle cells contract independently of each other. Cardiac muscle cells are linear like skeletal muscle cells but since they have to form a round structure, they are branched rather than strictly cylindrical in shape. The cells are connected to each other end to end by structure called intercalated discs. Smooth muscles is under involuntary control; do not have a sarcomere arrangement of thick & thin fibers like skeletal & cardiac cells; have less organized fiber arrangement of thick & thin filaments (attached directly to the cell membrane at structures called dense bodies, which serve the same function as a Z disc in a sarcomere). Muscle Atrophy & Muscular Diseases: Disuse atrophy occurs when a person cannot use a given muscle or group of muscles. Denervation atrophy, the loss or damage of nerves will prevent normal muscle contractions. Muscular Dystrophy or Duchenne's Muscular Dystrophy is a genetic disease that causes a loss of muscle fibers. This disease is linked to young males typically aged 3-5 years old. People with this disease are lacking a certain protein thus allowing too much Calcium (Ca+) into cell. This leads to cell death and damage that gets replaced with fibrous tissue and leads to scarring. Usually a person will not survive past age 30 as the disease afects the heart and muscles that perform breathing. Myasthenia gravis is an autoimmune disease, a condition caused when the immune system gets stupid and attacks body tissues instead of foreign invaders. In this case the immune system makes proteins called antibodies that bind to acetylcholine receptors. These antibodies block the attachment of acetylcholine which efectively prevents muscle contraction. This causes atrophy of muscle fibers. To treat this condition drugs that keep levels of ACh high are used to help stimulate contraction. Digestive System Functions: Ingestion Food enters into the system through the mouth; food is passed through a series of organs by muscle contraction; food is broken down by two kinds of processes: mechanical digestion, which occurs through chewing and mixing of food; chemical digestions, which occurs when food is mixed w/ digestive enzymes. These enzymes break chemical bonds & food is broken down to four basic components: carbohydrates, amino acids, fats, & nucleic acids. Absorption Once the food is broken down into individual carbohydrates, amino acids, fats, & nucleic acids, it is absorbed directly into the bloodstream Defecation Materials that cannot be digested/aren’t absorbed are packaged for disposal The digestive system is made up of a series of organs that sequentially process food for absorption. It consists of a long tube where the digestion & absorption take place; there are also several accessory organs that secrete substances into the main tube to aid in digestion. Gastrointestinal Tract (GI Tract or alimentary canal) has two parts. The upper GI tract consists of: mouth, pharynx & esophagus. The lower GI tract includes the stomach, small intestine, & large intestine Accessory organs are used to aid digestion & absorption of the GI tract, in the mouth includes the teeth, tongue, & salivary glands. Other accessory organs include the liver, gallbladder & pancreas. Mouth (Upper GI Tract): mouth, teeth, salivary glands Chewing/masticating grinds food & begins to mechanically digest it. The teeth cut, tear & then grind food into smaller bits to be swallowed. During this process the food is mixed w/ salivary amylase which begins the chemical breakdown of carbohydrates. Food is swallowed & becomes a bolus. Saliva serves to moisten & clean the oral cavity. It also serves to lubricate food & about 1-1.5 L is produced each day. It contains a couple of digestive enzymes: amylase degrades the common carbohydrate polymer starch, linguinal lipase breaks down fats. Some saliva enzymes don’t break down food, but have important functions: lysozyme has antibacterial efects that help control bacterial populations in the oral cavity, also found in tears Pharynx & Larynx (Upper GI Tract) When food is swallowed the bolus first passes into the throat/pharynx and then into the larynx. The mouth & pharynx can handle food & drink or air. In the larynx, there is a decision to be made b/c from this point food is directed into the esophagus while air gets passed to the trachea. There is a structure called the epiglottis that helps direct the food & air into the appropriate passageway. Esophagus (Upper GI Tract) Once past the epiglottis, food then moves down the esophagus towards the stomach. The esophagus runs through the chest cavity and into the abdominopelvic cavity where most of the digestive organs are stored. A respiratory muscle called the Diaphragm serves as a barrier between these two body cavities. The esophagus passes through the diaphragm at an opening called the esophageal hiatus and food enters the stomach through the esophageal sphincter. Conditions of the Esophagus: heartburn occurs when the esophageal sphincter stays open. Since the esophagus is not protected in the same way as the stomach, the HCl inside the stomach backwashes into and irritates the esophagus. The acid damages the esophagus lining and causes a burning feeling that gets mistaken for heart pain, thus acid reflux is often referred to as heartburn. A Hiatal hernia occurs when a small part of the stomach protrudes through the diaphragm at the esophageal hiatus. This condition may partially block the esophagus and prevent food from passing into the stomach. Peristalsis Muscle contractions move food through the tube of the digestive tract by the process of peristalsis. The structure of the digestive tract: The tube is surrounded by two layers of smooth muscle. One layer is arranged in a circular manner & the other runs the length of the tube, allowing for two specific types of contractions: 1. The circular layer contracts & pinches of the tube 2. The muscle running lengthwise contacts & pushes material forward in one direction Stomach (Lower GI Tract) The food bolus enters through the esophageal sphincter and is mixed into the stomach juices producing a liquid called Chyme. The epithelial lining of the stomach contains Gastric pits which are deep infoldings of the epithelial layer. A Gastric gland is located at the bottom of each pit. Here are found a variety of exocrine cells that secrete the gastric juice. Cells in the Stomach: 1. Pariental cells: secrete HCl & intrinsic factor. HCl breaks down food, particularly carbs). The intrinsic factor isn’t needed for food breakdown but it is needed to absorb Vitamin B12 in the small intestine. If intrinsic factor is not produced, the vitamin B12 won’t be absorbed. 2. Chief cells: secrete an enzyme called pepsinogen. HCl activates the inactive pepsinogen to its active form, pepsin. This is used to digest proteins. They also secrete gastric lipase which breaks down fats. 3. Mucous neck cell: produce a thick layer of alkaline mucous that prevents the gastric juices from coming into direct contact w/ stomach lining. Since Vitamin B12 is needed for red blood cell production, a lack of it will lead to anemia. This form is called Pernicious anemia and simply taking vitamin pills will not help. The vitamin cannot be absorbed. Only an injection of B12 directly into the bloodstream will be useful. A peptic ulcer occurs when the protective mucous lining of the stomach becomes degraded & thinned. Caused by: excessive stress, excessive alcohol consumption & smoking. Other causes include infections with Helicobacter Pylori which can infect the stomach and cause peptic ulcers. Small Intestine (Lower GI Tract) The small intestine is broken into 3 parts; Duodenum, Jejunum, Ileum. The stomach releases its contents into the first part of the small intestine, the Duodenum, through the pyloric sphincter, which is a valve/strong ring of smooth muscle that regulates stomach emptying. Since the small intestine is not as well protected from acid as the stomach, the first thing that must happen is the neutralization of the acidic chyme by Bicarbonate. The Duodenal glands secrete an alkaline mucous containing the bicarbonate that neutralizes gastric acids. Goblet cells also secrete mucous which also serves to protect the small intestine, and Paneth cells secrete lysozyme to help regulate the growth of bacteria in the small intestine. In order to maximize the surface area of the epithelial lining the small intestine, the inside surface is not smooth. The cells are found in big mounds or humps so that more cells can be packed into a linear foot of intestine. These structures are called villi and they line the length of the small intestine. Digestive enzymes are added from glands located in the lining of the small intestine. Other digestive enzymes are added to the small intestine from the Pancreas and Liver. For example, bile salts from the liver begin to emulsify fat. Once the food is broken down into individual carbohydrates, lipids, amino acids, and nucleic acids, these are absorbed into the bloodstream. Absorptive cells begin to move the digested food from the inside of the small intestine into the bloodstream using active transport. The apical surface of the absorptive cells are not flat but have many hair- like projections called microvilli. The microvilli are where the absorption takes place. They increase the surface area of each individual cell to increase the amount of transport that is done. Other accessory organs Pancreas has two kinds of cells: exocrine secrete digestive enzymes and endocrine secrete hormones involved in regulating digestion. About 1% of pancreatic cells, located in clusters called Islets of Langerhans, are endocrine. These secrete hormones like insulin, glucagon, & somatostatin. The other 99% of pancreatic cells (exocrine) secrete pancreatic juices. This includes sodium bicarbonate (HCO3) which bufers acidity of the chyme leaving the stomach. Others include: 1. Pancreatic amylase which breaks down carbs 2. Trypsin, chymotrypsin, carboxypeptidase all break down proteins 3. Pancreatic lipids break down fats 4. DNAse & RNAse are enzymes that break down nucleic acids Liver The liver secretes bile salts to aid in digestion. Bile salts help to emulsify fats or take a large mass of fat and break them down into smaller masses of fat. This efectively increases the surface area available to lipases. Bile salts travel down the bile duct into the small intestine. Liver functions: 1. Forms glycogen to store & regulate blood glucose which must be maintained to prevent serious diabetic complications including a coma 2. Metabolizes alcohol and removes drugs like antibiotics from the blood. 3. Excretes bilirubin into the bile. 4. Is involved in the destruction of RBC's when they get too old to be useful. 5. Detoxifies and removes poisons. It also converts ammonia to urea which is excreted by the kidneys. 6. Regulates lipid metabolism for energy production. 7. Produces most of the plasma proteins found in the blood. 8. Stores vitamins and minerals especially Iron. Health problems of the liver: 1. Jaundice is a disease that indicates there is a problem w/ the way the liver is functioning; caused by a buildup of bilirubin in certain tissues. Bilirubin is a waste product that is produced by breaking down old red blood cells. Bilirubin tends to accumulate in fatty tissue and gives it a yellow hue. This is especially visible as the whites of the eyes can turn yellow. Jaundice can be caused by excess production of bilirubin/blockage of the bile duct, liver damage, infection 2. Neonatal Jaundice - Newborns can also have underdeveloped livers that are not properly functioning. 3. Cirrhosis is scarring of the liver due to chronic inflammation. This inflammation can be caused by exposure to chemicals, liver parasites or alcoholism. 4. Hepatitis is caused by a viral infection. 5. Hep A: Infectious hepatitis - contracted through the oral-fecal virus transmission: essentially through ingestion of contaminated food or drink. 6. Hep B & C: Serum hepatitis - considered a sexually transmitted disease. Large Intestine (Lower GI Tract) Once the remaining materials enter the large intestine or colon, most of the useful nutrients have been absorbed into the blood stream. Any leftover materials that were not needed are concentrated by removing water and salts to form feces. The consistency of the feces depends on the amount of water left behind. Too much leads to diarrhea and too little to constipation. Salt absorption- Water content is controlled by salt absorption. Salts are removed from the large intestine which makes the environment outside the colon hypertonic. This causes the water inside the large intestine to leave and enter the bloodstream. Lactose intolerance- When someone is lactose intolerant it means they cannot break down lactose, a disaccharide. Bacteria- Many bacteria are also found in the colon. These produce certain beneficial products like Vitamin K. A high fiber diet provides indigestible food mass. This ensures that undigested materials keep moving at regular intervals as prolonged retention of feces irritates the colon lining and may lead to cancerous conditions. Conditions afecting GI tract Food poisoning & digestive diseases 1. Infections tend to take longer to show symptoms and are a result of an organism gaining entry to the small intestine where they multiply and cause problems. 2. Intoxications occur when someone ingests the bacterial toxins found in a food product. In this case there may in fact be no living organisms present, just their toxic remnants. Oral Fecal route of Disease: Transmission Diseases of this type are often spread by what is called the oral- fecal route. Food & water may contain bacteria that originate from a fecal source. Bacteria are excreted in feces and somehow transmitted to the oral cavity. This can happen in restaurants when employees don't take precautions when using the restroom. More commonly though, improperly cooked foods, like eggs or hamburger are a source of disease. In some places around the world people drink from the same river or lake that the cows defecate in. In some countries it's the most common cause of death. Either way contaminated food or drink are consumed and disease results. Common Microbial Infections: salmonella (typhoid fever), cholera, botulism, dysentery, hepatitis, polio
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