Digestive System PDF - Fall 2023

Digestive System Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023  Learning Outcomes: State the function of each organ of the gastrointestinal tract. Describe the structure of the gastrointestinal tract wall. Describe...

Digestive System Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023  Learning Outcomes: State the function of each organ of the gastrointestinal tract. Describe the structure of the gastrointestinal tract wall. Describe the structure of the stomach and small intestine and explain their role in digestion. Explain how carbohydrates, lipids, and proteins are processed by the small intestine. Explain the functions of the pancreas, liver, and gallbladder during digestion. Describe the structure, function and disorder of the large intestine. 2 ©2020 McGraw-Hill Education  Overview of Digestion 2 The organs are located within the gastrointestinal (GI) tract. Function—to hydrolyze, or break down, the macromolecules found in food. The subunit molecules (monosaccharides, amino acids, fatty acids, and glycerol) can cross plasma membranes using facilitated and active transport. The nutrients made available are transported by the blood to our cells. 3 ©2020 McGraw-Hill Education  Stages of Digestion 1 Ingestion—intake of food via the mouth. Digestion—mechanically or chemically breaking down foods into their subunits. Mechanical digestion—chewing in the mouth and contractions of smooth muscles in the stomach. Chemical digestion—digestive enzymes hydrolyze macromolecules into subunits. Begins in the mouth, continues in the stomach, and is completed in the small intestine. 4 ©2020 McGraw-Hill Education  Stages of Digestion 2 Movement—food is passed from one organ to the next, normally by contractions of smooth muscle called peristalsis. Absorption—movement of nutrients across the GI tract wall into the blood; they are then delivered to cells. Elimination—removal of indigestible wastes. Defecation. 5 ©2020 McGraw-Hill Education  Wall of the Digestive Tract Lumen—open area of a hollow organ or vessel; in the GI tract, it contains food or feces. Layers: Mucosa—innermost layer; produces mucus for protection; also produces digestive enzymes. Submucosa—loose connective tissue; contains blood vessels, lymphatic vessels, and nerves. Muscularis—made of 2 layers of smooth muscle (inner, circular layer, and an outer, longitudinal layer) that move food along the GI tract. Serosa—outer lining; is part of the peritoneum. 6 ©2020 McGraw-Hill Education  Check Your Progress Describe the processes that occur during the digestive process. Identify the four layers of the GI tract from the lumen outward. 7 ©2020 McGraw-Hill Education  The Stomach 1 Stores food, starts digestion of proteins, and of controls movement food into the small intestine. Does not absorb nutrients. However, it does absorb alcohol, because alcohol is fat- soluble and can pass through membranes easily. There are three layers of muscle in the muscularis layer (instead of two) to help in mechanical digestion. Circular, longitudinal, and third oblique layer. 8 ©2020 McGraw-Hill Education  The Stomach 2 The mucosa has deep folds called rugae. The mucosa also has gastric pits, which contain gastric glands. The gastric glands produce gastric juice, which contains: Pepsin—digests proteins. Hydrochloric acid (HCl)—pH of 2. Kills bacteria and activates pepsin. Mucus. Normally, the stomach empties in 2–6 hours. Chyme—a mixture of food and gastric juice. Pyloric sphincter—allows only a small amount of chyme to enter the small intestine at a time. 9 ©2020 McGraw-Hill Education  Heartburn (GERD) The lining of the esophagus is thinner than the lining of the stomach; if chyme enters the esophagus, it produces a burning sensation. Gastroesophageal reflux disease (GERD)—chronic heartburn. Can be caused by pregnancy and excess fat pushing on the stomach. 10 ©2020 McGraw-Hill Education  Digestion Is Completed in the Small Intestine 1 Small intestine. Pancreas—secretes digestive enzymes through a duct into the duodenum, the first portion of the small intestine. Another duct brings bile from the liver and gallbladder into the duodenum. Bile emulsifies fat. Lipase produced by the pancreas, it hydrolyzes fats into glycerol and fatty acids. 11 ©2020 McGraw-Hill Education  Digestion Is Completed in the Small Intestine 2 Pancreatic amylase—produced by the pancreas, secreted into the duodenum. Digests carbohydrates. Trypsin—produced by the pancreas, secreted into the duodenum. Digests proteins, so is a protease—a class of enzymes that digest proteins. Pancreatic juice contains sodium bicarbonate, which neutralizes acidic chyme. 12 ©2020 McGraw-Hill Education  Nutrients Are Absorbed in the Small Intestine 1 The mucosa contains fingerlike projections called villi (singular, villus). The cells that cover the villi have microvilli. Give the villi a fuzzy “brush border”. Contain brush border enzymes that complete digestion. These two structures greatly increase the surface area of the small intestine for absorption of nutrients. 13 ©2020 McGraw-Hill Education  Nutrients Are Absorbed in the Small Intestine 2 Nutrients are absorbed into the villi, which contain blood capillaries and a small lymphatic capillary called a lacteal. Monosaccharides and amino acids enter the blood capillaries of a villus. Glycerol and fatty acids form lipoprotein droplets called chylomicrons, which then enter a lacteal. After nutrients are absorbed, they are eventually carried to all the cells of the body by the blood. 37 ©2020 McGraw-Hill Education  Digestion and Absorption of Organic Nutrients Access the text alternative for these images 38 ©2020 McGraw-Hill Education  Major Digestive Enzymes 1 Major Digestive Enzymes: Carbohydrate Digestion. Enzyme Produced By Site of Action Optimum pH Digestion Salivary amylase Salivary glands Mouth Neutral Starch + H2O → maltose Pancreatic amylase Pancreas Small intestine Basic Starch + H2O → maltose Maltase Small intestine Small intestine Basic Maltose + H2O → glucose + glucose Lactase Small intestine Small intestine Basic Lactose + H2O →"glucose + galactose Major Digestive Enzymes: Protein Digestion. Enzyme Produced By Site of Action Optimum pH Digestion Pepsin Gastric glands Stomach Acidic Protein + H2O → peptides Trypsin Pancreas Small intestine Basic Protein + H2O → peptides Peptidases Small intestine Small intestine Basic Protein + H2O → amino acids Major Digestive Enzymes: Nucleic Acid Digestion. Enzyme Produced By Site of Action Optimum pH Digestion Nuclease Pancreas Small intestine Basic RNA and DNA + H2O → nucleotides Nucleosidases Small intestine Small intestine Basic Nucleotide + H2O→ base + sugar + phosphate Major Digestive Enzymes: Fat Digestion. Enzyme Produced By Site of Action Optimum pH Digestion Lipase Pancreas Small intestine Basic Fat droplet + H2O → monoglycerides + 16 ©2020 McGraw-Hill Education fatty acids  Lactose Intolerance Lactose intolerance. Lactose is the primary sugar in milk. Lactase—the brush border enzyme that digests lactose. Characterized by diarrhea, gas, bloating, and abdominal cramps after ingesting milk and other dairy products. Diarrhea occurs because the undigested lactose causes fluid retention in the small intestine. Gas, bloating, and cramps occur when bacteria break down the lactose anaerobically. 17 ©2020 McGraw-Hill Education  Check Your Progress Summarize the differences in how carbohydrates, proteins, and fats are digested and absorbed by the small intestine. 18 ©2020 McGraw-Hill Education  The Accessory Organs 1 Pancreas Located behind the stomach. Most pancreatic cells produce pancreatic juice, which enters the duodenum via the pancreatic duct. Contains sodium bicarbonate and digestive enzymes. 19 ©2020 McGraw-Hill Education  The Accessory Organs 2 Also an endocrine gland; secretes the hormone insulin when the blood glucose levels rise. Type 1 diabetes—not enough insulin. Normally diagnosed in childhood. Type 2 diabetes—the body’s cells are insulin- resistant. Normally occurs in adulthood. Risk factors: obesity, inactivity, family history. 20 ©2020 McGraw-Hill Education  The Liver 1 Liver. The largest gland in the body. Lies mainly in the upper right abdominal cavity, under the diaphragm. Lobules—structural and functional units. The hepatic portal vein brings blood to the liver from the GI tract. The lobules filter this blood, removing poisonous substances. 21 ©2020 McGraw-Hill Education  The Liver 2 Regulates blood cholesterol levels. Produces bile, which contains bile salts, water, cholesterol, and bicarbonate. Involved in blood glucose homeostasis. Stores glucose as glycogen; when blood glucose is low, it releases glucose by breaking down glycogen. Produces plasma proteins such as albumins and fibrinogen, from amino acids. Detoxifies blood by removing and metabolizing poisonous substances Stores iron (Fe2+), the water-soluble vitamin B12, and the fat-soluble vitamins A, D, E, and K. 22 ©2020 McGraw-Hill Education  The Gallbladder Gallbladder. Pear-shaped organ just below the liver. Stores bile. 23 ©2020 McGraw-Hill Education  Liver Disorders Liver disorders: hepatitis and cirrhosis. Liver disease can cause bile pigments to leak into the blood, causing jaundice. Yellowish tint to the whites of the eyes and the skin. Hepatitis. Inflammation of the liver. Has different forms. 24 ©2020 McGraw-Hill Education  Hepatitis Hepatitis, continued. Hepatitis A—usually acquired from sewage- contaminated drinking water and food. Hepatitis B—usually from sexual contact, but also from blood transfusions or contaminated needles. More contagious than the AIDS virus and is spread in the same way. Vaccines are available for hepatitis A and B. Hepatitis C—usually acquired by infected blood. Can lead to chronic hepatitis, liver cancer, and death. 25 ©2020 McGraw-Hill Education  Cirrhosis Chronic disease; first, liver becomes fatty, and then filled with fibrous scar tissue. Often seen such in viral infectious diseases like hepatitis, excess consumption of alcohol and overload of iron in the hepatic tissue. The liver can regenerate and recover if the rate of regeneration exceeds the rate of damage. During liver failure there may not be enough time to let the liver heal so will need a liver transplantation. 26 ©2020 McGraw-Hill Education  Check Your Progress Name and describe the functions of three main accessory organs that assist with the digestive process. 59 ©2020 McGraw-Hill Education  The Large Intestine 1 Large intestine—includes the cecum, the colon, the rectum, and the anal canal. Larger in diameter than the small intestine, but it is shorter in length. Cecum—the first portion. Vermiform appendix—projection off of the cecum. Fights infections. Appendicitis—inflamed appendix; can cause peritonitis, a life- threatening infection of the peritoneum. 61 ©2020 McGraw-Hill Education  The Large Intestine 2 Colon—includes the ascending colon, which goes up the right side of the body; transverse colon, which crosses the abdominal cavity; descending colon, which passes down the left side; and the sigmoid colon, which enters the rectum, the last portion of the large intestine. The rectum opens at the anus, where defecation, the expulsion of feces, occurs. 63 ©2020 McGraw-Hill Education  Functions of the Large Intestine 1 Absorbs vitamins produced by intestinal flora, (the bacteria that inhabit the intestine.) Bacteria break down indigestible material and produce B- complex vitamins and vitamin K. Forms feces. Bacteria and dietary fiber (indigestible remains) make up the solid wastes. Defecation—ridding the body of feces. Peristalsis forces feces into the rectum. Can inhibit defecation by contracting the external anal sphincter, which is made of skeletal muscle. 64 ©2020 McGraw-Hill Education  Disorders of the Colon and Rectum 1 Diarrhea—increased peristalsis and failure to absorb water from feces, due to either an infection or nervous stimulation. Constipation—dry, hard feces; may be controlled with water and fiber. Diverticulosis—pouches; weak spots in the muscularis layer. 67 ©2020 McGraw-Hill Education  Diverticulosis Diverticulosis. A condition in which the mucosa of any part of the GI tract (usually the large intestine) pushes through the other layers and forms pouches where food collects. Diverticulitis—when the pouches become infected. This happens in 10–25% of people with diverticulosis. 32 ©2020 McGraw-Hill Education  Bowel Disease Inflammatory bowel disease (IBD)—chronic diarrhea, abdominal pain, fever, and weight loss. Irritable bowel syndrome (IBS)—contractions of the muscularis cause abdominal pain, constipation, and diarrhea. The underlying cause is not known. 33 ©2020 McGraw-Hill Education Skeletal System- Part 1 Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023  Learning Outcomes: State the functions of the skeletal system. Describe the structure of a long bone. Types of cartilage found in the body and the function for each. Identify and explain about the bones of the skull, vertebral column, and rib cage. 2 ©2020 McGraw-Hill Education  Skeletal System 2 The skeletal system consists of two types of connective tissue: bone and cartilage. Ligaments, formed of fibrous connective tissue, join the bones. Functions of the skeleton: Supports the body. Working with the muscular system, moves the body Protection. Skull protects the brain, rib cage protects the heart and lungs, the vertebrae protect the spinal cord. Produces blood cells. Stores minerals (calcium and phosphate) and fat. 3 ©2020 McGraw-Hill Education  Anatomy of a Long Bone 1 Diaphysis—shaft of the bone. Medullary cavity—inside the diaphysis; its walls are made of compact bone. The medullary cavity is lined with the endosteum and is filled with yellow bone marrow, which stores fat. Epiphysis —expanded end of a long bone. Composed of spongy bone that contains red bone marrow, where blood cells are made. 4  Anatomy of a Long Bone 2 The epiphyses are coated with a thin layer of hyaline cartilage, which is also called articular cartilage, because it occurs at a joint. Metaphysis—between the epiphysis and diaphysis. Contains the epiphyseal plate, a region of cartilage that allows for bone growth. Periosteum—connective tissue covering all bones; continuous with ligaments and tendons. 5 ©2020 McGraw-Hill Education  Bone 1 There are two types of bone tissue: compact and spongy. Compact bone is highly organized and composed of tubular units called osteons. Osteocytes are bone cells; they lie in lacunae (singular, lacuna), tiny chambers arranged in concentric circles around a central canal. Matrix fills the space between the rows of lacunae. 6 ©2020 McGraw-Hill Education  The Anatomy of a Long Bone Access the text alternative for these images 9 ©2020 McGraw-Hill Education (photos) (compact bone): ©Ed Reschke; (osteocyte): ©Biophoto Associates/Science Source  Bone 2 Tiny canals called canaliculi (singular, canaliculus) connect the lacunae with one another and with the central canal. Osteocytes stay in contact with each other in the canaliculi. They exchange nutrients and wastes through gap junctions that connect adjacent osteocytes. 8 ©2020 McGraw-Hill Education  Bone 3 Spongy bone contains numerous thin plates called trabeculae. Although lighter than compact bone, spongy bone is still designed for strength. Red bone marrow—in the spaces of spongy bone. Produces all types of blood cells. Osteocytes of spongy bone are irregularly placed within the trabeculae. 9 ©2020 McGraw-Hill Education  Cartilage 1 Cartilage—not as strong as bone but is more flexible. Matrix contains collagen and elastic fibers. Chondrocytes—cartilage cells; lie within lacunae. Has no nerves or blood vessels; relies on neighboring tissues for nutrient and waste exchange. This makes it slow to heal. There are three types of cartilage: hyaline, fibrocartilage, and elastic cartilage. 10 ©2020 McGraw-Hill Education  Cartilage 2 Locations of cartilage. Hyaline cartilage: ends of long bones, nose, ends of ribs, larynx, and trachea. Fibrocartilage: disks between vertebrae and in the knee. Elastic cartilage: ear flaps 11 ©2020 McGraw-Hill Education  Fibrous Connective Tissue Fibrous connective tissue. Made of rows of fibroblasts separated by bundles of collagenous fibers. Makes up ligaments and tendons. Ligaments connect bone to bone. Tendons connect muscle to bone at a joint (also called an articulation). 12 ©2020 McGraw-Hill Education  Check Your Progress List the functions of the skeletal system. Summarize the structure of a long bone by describing the differences in structure. Describe the three types of cartilage and list where they are found in the body. 13 ©2020 McGraw-Hill Education  Bones of the Axial Skeleton 2 The 206 bones of the skeleton are classified as the axial or appendicular skeleton. Axial skeleton—midline of the body. Mainly consists of the skull, vertebral column, and the rib cage. 1. The skull. Formed by the cranium and the facial bones. Cranium. Contains and protects the brain. In adults, made of eight bones. In newborns, cranial bones are joined by membranous fontanels. Usually close by the age of 16 months. 14 ©2020 McGraw-Hill Education  The Axial and Appendicular Skeletons 15 ©2020 McGraw-Hill Education  The Skull 2 Bones: frontal, parietal, occipital, temporal, sphenoid, ethmoid. Foramen magnum—a hole in the occipital bone through which the spinal cord passes. External auditory canal—in each temporal bone; leads to the middle ear. The sphenoid completes the sides of the skull and contributes to forming the orbits (eye sockets). The ethmoid bone also helps form the nasal septum. 16 ©2020 McGraw-Hill Education  The Vertebral Column 1 2. Vertebral column—consists of 33 vertebrae. There are four curvatures that provide more strength for an upright posture than a straight column. Scoliosis—abnormal sideways curvature of the spine. Kyphosis—abnormal posterior curvature; “hunchback.” Lordosis—abnormal anterior curvature; “swayback.” 17 ©2020 McGraw-Hill Education  The Vertebral Column 2 Vertebral canal—in the center of the column; the spinal cord passes through. Intervertebral foramina (singular, foramen, “a hole”) on each side of the column; spinal nerves travel through. Spinal nerves control skeletal muscle contraction, among other things. If the spinal cord and/or spinal nerves are injured, there can be paralysis or even death. 18 ©2020 McGraw-Hill Education  Types of Vertebrae Types of vertebrae. Cervical vertebrae—in the neck. Atlas—first cervical vertebra; holds up the head. Movement permits the “yes” motion of the head. Axis—second cervical vertebra. Named because it rotates around the long axis of the body when we shake the head “no.” 19 ©2020 McGraw-Hill Education  The Vertebral Column Access the text alternative for these images 20 ©2020 McGraw-Hill Education  Intervertebral Disks 1 Composed of fibrocartilage. Prevent the vertebrae from grinding. Absorb shock caused by movements such as running, jumping, and even walking. Allows the vertebrae to move as we bend forward, backward, and from side to side. Become weakened with age and can rupture. Pain results if a disk presses against the spinal cord and/or spinal nerves. 21 ©2020 McGraw-Hill Education  The Rib Cage 3. Rib cage (thoracic cage)— composed of the thoracic vertebrae, the ribs and their associated cartilages, and the sternum. Part of the axial skeleton. Protects the heart and lungs. Swings outward and upward upon inspiration and then downward and inward upon expiration. 22 ©2020 McGraw-Hill Education  The Ribs 1 There are 12 pairs; all connect directly to the thoracic vertebrae in the back. Curve outward and then forward and downward. True ribs—ribs 1 to 7; connect directly to the sternum by means of a long strip of hyaline cartilage called costal cartilage. False ribs—ribs 8 to 12; their costal cartilage does not connect directly to the sternum. Floating ribs—ribs 11 and 12; they have no connection with the sternum. Sternum (breastbone) Along with the ribs, it helps protect the heart and lungs. 23 ©2020 McGraw-Hill Education  Check Your Progress List the bones of the axial skeleton. Describe the various types of vertebrae. 24 ©2020 McGraw-Hill Education Skeletal System- Part II Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023  Learning Outcomes: List the three types of joints. Describe the structure and operation of a synovial joint. Summarize the process of ossification and list the types of cells involved. Describe the process of bone remodeling. Explain the steps in the repair of bone. 2 ©2020 McGraw-Hill Education  Articulations 2 Articulations (joints) Where bones come together. Are classified as fibrous, cartilaginous, or synovial. Fibrous joints are immovable. Cartilaginous joints are Slightly movable. Synovial joints are freely movable. 3 ©2020 McGraw-Hill Education  Types of Synovial Joints Types of synovial joints: Ball-and-socket joints—allow movement in all planes, even rotational movement. That is, the hips and shoulders. Hinge joints—permit movement in only one direction. That is, the elbow and knee. 52 ©2020 McGraw-Hill Education  Synovial Joints Allow for a Variety of Movement Access the text alternative for these images 53 ©2020 McGraw-Hill Education  Check Your Progress List the three major types of joints. Describe the different movements of synovial joints, and give an example of each in the body. 6 ©2020 McGraw-Hill Education  Bone Growth and Homeostasis 2 Cells involved in bone growth, remodeling, and repair: Osteoblasts—bone-forming cells. Secrete the organic matrix of bone and promote the deposition of calcium salts into the matrix. Osteocytes—mature bone cells. When osteoblasts surround themselves with calcified matrix, they become osteocytes within lacunae. Osteoclasts—bone-absorbing cells. Break down bone; return calcium and phosphate to the blood. Throughout life, osteoclasts remove the matrix of bone and osteoblasts build it up. 7 ©2020 McGraw-Hill Education  Intramembranous Ossification Ossification—the formation of bone. Bones form during embryonic development in two distinctive ways: 1. Intramembranous ossification—forms flat bones (that is, bones of the skull). Bones develop between sheets of fibrous connective tissue. Osteoblasts in the periosteum carry out further ossification. Trabeculae form and fuse into compact bone, which surrounds the spongy bone inside. 8 ©2020 McGraw-Hill Education  Endochondral Ossification 2. Endochondral ossification—forms most bones (that is, long bones like the tibia). Calcified bone matrix replaces the hyaline cartilage models of the bones. Bone formation spreads from the center of the bone to the ends. Bone Growth by Endochondral Ossification 9 ©2020 McGraw-Hill Education  Steps of Endochondral Ossification 1 The steps of endochondral ossification: The cartilage model: in the embryo, chondrocytes form cartilage models (hyaline cartilage shaped like the future bones). The bone collar: osteoblasts secrete the matrix, which then calcifies. The result is a bone collar made of compact bone, which covers the diaphysis. 10 ©2020 McGraw-Hill Education  Steps of Endochondral Ossification 2 The primary ossification center: blood vessels bring osteoblasts to a region called a primary ossification center—the first center for bone formation. The medullary cavity and secondary ossification sites: spongy bone in the diaphysis is absorbed by osteoclasts, forming the medullary cavity. Shortly after birth, secondary ossification centers form in the epiphyses. 11 ©2020 McGraw-Hill Education  Steps of Endochondral Ossification 3 The epiphyseal (growth) plate: a band of cartilage remains between the primary ossification center and each secondary center. The limbs keep increasing in length as long as the epiphyseal plates are present. Cartilage is now present at two locations: the epiphyseal (growth) plate and articular cartilage, which covers the ends of long bones. 12 ©2020 McGraw-Hill Education  The Epiphyseal Plate The epiphyseal plate contains four layers: The layer nearest the epiphysis is the resting zone, where cartilage remains. The next layer is the proliferating zone, in which chondrocytes are producing new cartilage cells. In the third layer, the degenerating zone, the cartilage cells are dying off. In the fourth layer, the ossification zone, bone is forming, which increases the length of the bone. 13 ©2020 McGraw-Hill Education  Increasing Bone Length Access the text alternative for these images 14 ©2020 McGraw-Hill Education  Final Size of the Bones Final size of the bones. When the epiphyseal plates close, bone lengthening can no longer occur. Several hormones play an important role in bone growth: vitamin D, growth hormone, thyroid hormone, and sex hormones. 15 ©2020 McGraw-Hill Education  Hormones Affect Bone Growth 1 Vitamin D—formed in the skin when exposed to sunlight. Is converted to a hormone that is necessary for absorption of calcium from food. Low vitamin D levels in children causes rickets. Bone deformities 16 ©2020 McGraw-Hill Education  Hormones Affect Bone Growth 2 Growth hormone (GH)—stimulates bone growth. Need concurrent action of thyroid hormone to stimulate metabolism. Dwarfism—too little GH in childhood. Gigantism—excess GH in childhood. Acromegaly—excess GH in adults. Excessive growth of bones in the hands and face. Sex hormones—increase growth during adolescence. 17 ©2020 McGraw-Hill Education  Bone Remodeling and Calcium Homeostasis 1 Bone remodeling—osteoclasts break bone down, osteoblasts build it up. Recycles 18% of bone each year. Paget disease—new bone is generated at a faster-than-normal rate. Produces softer and weaker bones. Can cause bone pain, deformities, and fractures. 18 ©2020 McGraw-Hill Education  Bone Remodeling and Calcium Homeostasis 2 Calcium homeostasis. If blood calcium rises, some of the excess is deposited in bones. If blood calcium drops, calcium is removed from bones to bring it up to normal. 19 ©2020 McGraw-Hill Education  Calcium Homeostasis 1 Parathyroid hormone (PTH). Stimulates osteoclasts to dissolve bone. Promotes calcium absorption in the small intestine and kidney, increasing blood calcium levels. Vitamin D. Needed for the absorption of Ca2+ from the digestive tract. 20 ©2020 McGraw-Hill Education  Calcium Homeostasis 2 Calcitonin. Has opposite effects as PTH. Estrogen. Increases the number of osteoblasts. The reduction of estrogen in older women can cause osteoporosis. 21 ©2020 McGraw-Hill Education  Osteoporosis. Bones are weakened due to decreased bone mass. Skeletal mass increases until age 30. After that, there is an equal rate of formation and breakdown of bone mass until age 50. Then, reabsorption begins to exceed formation, and the total bone mass slowly decreases. Risk factors include: women, family history, early menopause, smoking, diet low in calcium, excessive caffeine or alcohol consumption. 22 ©2020 McGraw-Hill Education  Bone Repair 1 Steps of bone repair: Hematoma—forms 6 to 8 hours after the fracture. Blood clot between broken bones. Fibrocartilaginous callus—forms in 3 weeks. Fibrocartilage callus between broken bones. Bony callus—forms in 3 to 4 months. Cartilaginous callus turns into bone. Remodeling. Osteoblasts build new compact bone at the periphery, osteoclasts absorb the spongy bone, creating a new medullary cavity. 23 ©2020 McGraw-Hill Education  Bone Repair Following a Fracture 24 ©2020 McGraw-Hill Education  Bone Repair 2 Types of bone fractures: Complete—the bone is broken clear through. Incomplete—the bone is not separated into two parts. Simple—it does not pierce the skin. Compound—it does pierce the skin. Impacted—the broken ends are wedged into each other. Spiral—the break is ragged due to twisting of the bone. 25 ©2020 McGraw-Hill Education  Blood Cells Are Produced in Bones There are two types of marrow: yellow and red. Fat is stored in yellow bone marrow. Red bone marrow is the site of blood cell production. 26 ©2020 McGraw-Hill Education  Check Your Progress Summarize the stages in the repair of bone. Explain how the skeletal system is involved in calcium homeostasis. 27 ©2020 McGraw-Hill Education Cardiovascular System Heart and Blood Vessels –Part II Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023 Learning Outcomes: Understand how the pulse relates to heart rate. Distinguish between systolic and diastolic pressure. Explain how blood flow and pressure differs in veins, arteries, and capillaries. Compare blood flow in the pulmonary and systemic circuits. Describe the processes that move materials across the walls of a capillary. Explain the underlying causes of cardiovascular disease in humans. Summarize how advances in medicine can treat cardiovascular disorders. 2 ©2020 McGraw-Hill Education  Features of the Cardiovascular System 2 Blood Pressure—the pressure that blood exerts against a blood vessel wall. Is highest in the aorta, right next to the heart; it gradually decreases as it flows through the vessels in the body. Pulse—surge of blood into an artery causes the walls to stretch, and then recoil. Usually measured in the radial artery at the wrist or carotid artery in the neck. A measurement of the heart rate; averages 60–80 beats per minute. 3 ©2020 McGraw-Hill Education  Blood Flow Is Regulated 1 Blood Pressure Contraction of ventricles creates blood pressure, which propels blood through the arteries. Measured with a sphygmomanometer, in the brachial artery of the arm. 4 ©2020 McGraw-Hill Education  Blood Flow is Regulated 2 Blood Pressure Systolic pressure—the highest pressure; when blood is ejected from the heart. Diastolic pressure—the lowest pressure; when the ventricles relax. Average is 120/80 mmHg (systolic/diastolic). Hypertension—high blood pressure. Hypotension—low blood pressure. 5 ©2020 McGraw-Hill Education  Normal Values for Adult Blood Pressure Normal Values for Adult Blood pressure* Top Number Bottom Number (Systolic) (Diastolic) Hypotension Less than 95 Less than 50 Normal Below 120 Below 80 Prehypertension 120 to 139 80 to 89 Stage 1 hypertension 140 to 159 90 to 99 Stage 2 hypertension 160 or more 100 or more Hypertensive crisis Higher than 180 Higher than 110 (emergency care needed) *Blood pressure values established by the American Heart Association (www.heart.org). 6 ©2020 McGraw-Hill Education  Blood Flow Blood flow Blood pressure decreases as it flows away from the heart. Is slowest in the capillaries to increase the exchange of gases, nutrients, and wastes. Is adjusted by the precapillary sphincters. 7 ©2020 McGraw-Hill Education  Blood Flow 2 Blood flow Blood pressure is very low in the veins, so doesn’t contribute much to the movement of blood. Venous return is dependent on three additional factors: Skeletal muscle pump (dependent on skeletal muscle contraction). Respiratory pump (dependent on The Skeletal Muscle Pump breathing). Valves present in veins. 8 ©2020 McGraw-Hill Education  Check Your Progress Explain what the pulse rate of a person indicates. Compare and contrast the characteristics of blood flow in the veins, arteries, and capillaries. Explain why valves are needed in the veins. 9 ©2020 McGraw-Hill Education Two Cardiovascular Pathways 2 Blood flows in two circuits: the pulmonary circuit and systemic circuit. Pulmonary circuit circulates blood through the lungs. Systemic circuit circulates blood through the body tissues. Overview of the Cardiovascular System 10 ©2020 McGraw-Hill Education The Pulmonary Circuit: Exchange of Gases 1 Pulmonary circuit: Right atrium pumps deoxygenated blood into the right ventricle, which pumps it into the pulmonary trunk. The pulmonary trunk splits into right and left pulmonary arteries, which go to the lungs. In the lungs, the pulmonary arteries branch into arterioles, which lead to capillaries. This is where gas exchange occurs. 11 ©2020 McGraw-Hill Education The Pulmonary Circuit: Exchange of Gases 2 The pulmonary capillaries lead to venules, which merge into the pulmonary veins. The four pulmonary veins empty into the left atrium. The pulmonary arteries carry oxygen-poor blood; the pulmonary veins carry oxygen-rich blood. 12 ©2020 McGraw-Hill Education  The Systemic Circuit: Exchanges with Interstitial Fluid 1 The systemic circuit: The left ventricle pumps blood into the aorta, which gives off branches to all the tissues of the body. Arteries branch into (eventually) arterioles, which lead to capillaries. Capillaries lead to venules, which drain into veins, which lead to the superior and inferior vena cavae. The vena cavae empty into the right atrium. 13 ©2020 McGraw-Hill Education  The Systemic Circuit: Exchanges with Interstitial Fluid 2 The systemic circuit Usually, blood flows from the aorta into an artery that supplies an organ, then through veins back to one of the vena cavae. From aorta > renal artery > kidney > renal vein > inferior vena cava. However, there are special routes that don’t follow this pathway. Eg: the hepatic portal system. 14 ©2020 McGraw-Hill Education  Hepatic Portal System: Specialized for Blood Filtration Hepatic portal vein: Brings nutrient-rich blood from the digestive tract to the liver. The liver synthesizes blood proteins from the amino acids in the hepatic portal vein and stores the glucose as glycogen. The liver also removes toxins and pathogens that enter the blood through the digestive system. Blood is drained from the liver into the hepatic veins, which drain into the inferior vena cava. ©2020 McGraw-Hill Education 15  Exchange at the Capillaries 2 Two forces drive fluid in and out of capillaries: Blood pressure drives fluid out of the capillary, mainly at the arterial end of the capillary bed. This fluid contains everything that blood contains except cells and plasma proteins. 16 ©2020 McGraw-Hill Education  The Movement of Solutes in a Capillary Bed Osmotic pressure draws water into the capillary by osmosis, mostly at the venule end. Some tissue fluid enters lymphatic capillaries and becomes lymph, which is eventually returned to the cardiovascular system. Access the text alternative for these images 60 ©2020 McGraw-Hill Education ©Scimat/Science Source  Check Your Progress Explain what happens to the excess fluid created during capillary exchange. Describe the exchange of materials across the walls of a capillary. 18 ©2020 McGraw-Hill Education  Cardiovascular Disorders 2 Cardiovascular disease (CVD). Leading cause of early death in Western countries. Disorders of the blood vessels. Hypertension (high blood pressure) and atherosclerosis often lead to a stroke, heart attack, or aneurysm. 19 ©2020 McGraw-Hill Education  Hypertension Hypertension (high blood pressure). A systolic pressure of 140 or greater or a diastolic pressure of 90 or greater. A “silent killer” because there are few symptoms until it causes kidney failure, a heart attack, or stroke. Treated with diuretics, which increase the production of urine, and other drugs. 20 ©2020 McGraw-Hill Education  Atherosclerosis Atherosclerosis. A buildup of atherosclerotic plaque in the walls of blood vessels. Plaques narrow blood vessel diameter, decreasing blood supply to tissues. Can cause clots to form in the roughened walls of arteries. Thrombus—a clot that is stationary. Embolus—a clot that detaches and moves to distant sites. Thromboembolism—an embolus that has become lodged in a blood vessel. 21 ©2020 McGraw-Hill Education  Coronary Arteries and Plaque 22 ©2020 McGraw-Hill Education ©Biophoto Associates/Science Source  Stroke Stroke (cerebrovascular accident, or CVA). Occurs when a cranial artery is blocked or bursts. Part of the brain dies dues to lack of oxygen. Symptoms may include numbness of hands or face, difficulty speaking, and inability to see in one eye. 23 ©2020 McGraw-Hill Education  Heart Attack Myocardial infarction (MI, or heart attack). Part of the heart dies due to lack of oxygen. Caused by a blocked coronary artery. It can begin with angina pectoris, pain in the chest from a partially blocked coronary artery. Can be treated with drugs that dilate blood vessels. 24 ©2020 McGraw-Hill Education  Treating Clogged Arteries Treating clogged arteries. Coronary bypass operation: a vein from the leg is taken and used to bypass a clogged artery. Gene therapy—injection of the gene for vascular endothelial growth factor (VEGF) induces the growth of new vessels. Then there is no need for bypass surgery. Angioplasty: a tube is inserted into the clogged artery to insert a stent—a mesh cylinder to hold it open. Stents are usually coated in drugs to dissolve blockages. 25 ©2020 McGraw-Hill Education  Heart Failure Heart failure. The heart no longer pumps properly. Treatments: Implantable cardioverter-defibrillator (ICD) corrects an irregular rhythm. Heart transplant. Injection of stem cells to repair damaged heart. Left ventricular assist device (LVAD)—battery-powered pump to assist the heart. Total artificial heart (TAH) —temporary solution. 27 ©2020 McGraw-Hill Education  An Artificial Heart Access the text alternative for these images 74 ©2020 McGraw-Hill Education ©SynCardia Systems, Inc. Cardiovascular System Heart and Blood Vessels –Part I Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023  Learning Outcomes: Identify the two components of the cardiovascular system. Summarize the functions of the cardiovascular system. Explain the purpose of the lymphatic system in circulation. Describe the structure and function of the three types of blood vessels and blood flow regulation in each. Identify the chambers of the human heart and describe the flow of blood through the human heart. 2 ©2020 McGraw-Hill Education  Overview of the Cardiovascular System 2 Cardiovascular system. Made up of the heart and blood vessels. The heart pumps blood through blood vessels. It brings nutrients to cells and helps get rid of wastes. Exchange of substances occurs through interstitial fluid. 3 ©2020 McGraw-Hill Education  Functions of the Cardiovascular System Functions of the cardiovascular system. Transport: oxygen, carbon dioxide, and other waste products, nutrients, and hormones. Protection: cells of the immune system are transported to help protect the body from infection. Regulation: maintains homeostasis of a variety of the body’s conditions. Eg: pH balance, electrolyte levels, temperature. 4 ©2020 McGraw-Hill Education  Lymphatic System Lymphatic system assists the cardiovascular system by collecting excess tissue fluid and returning it to the blood. When fluid enters the lymphatic vessels it is called lymph. 5 ©2020 McGraw-Hill Education  Check Your Progress Describe the two parts of the cardiovascular system. Summarize the functions of the cardiovascular system. Explain how the lymphatic system interacts with the cardiovascular system. 6 ©2020 McGraw-Hill Education  The Types of Blood Vessels 2 There are three types of blood vessels: arteries, veins, and capillaries. Artery—carries blood away from the heart. Their walls have 3 layers: Endothelium—the thin, inner epithelium. Middle layer—smooth muscle and elastic tissue. Allows arteries to expand and recoil. Outer layer—connective tissue. 7 ©2020 McGraw-Hill Education  Structure of Arteries and Veins 8 ©2020 McGraw-Hill Education ©Ed Reschke  Arterioles Arterioles. Small arteries. Middle layer has mostly smooth muscle. It contracts to constrict the vessel, reducing blood flow and raising blood pressure. When relaxed, the vessel dilates, increasing blood flow and reducing blood pressure. 9 ©2020 McGraw-Hill Education  The Capillaries: Exchange Capillaries. Microscopic vessels between arterioles and venules. Walls of capillaries are made only of endothelium. Form capillary beds where gas, nutrient, and waste exchange occurs. Have precapillary sphincters, which control blood flow through the capillary bed. 10 ©2020 McGraw-Hill Education  Structure of a Capillary Bed Access the text alternative for these images 13 ©2020 McGraw-Hill Education (capillary bed): ©Steve Gschmeissner/Science Photo Library/Alamy  The Veins: To the Heart 1 Venules—small veins that receive blood from the capillaries. Veins carry blood toward the heart. Venule and vein walls have the same 3 layers as arteries, but less smooth muscle in the middle layer. Veins that carry blood against gravity have valves to keep blood flowing toward the heart. Walls of veins are thinner than arteries so they can expand to hold more blood. At any one time, they store 70% of the blood. 12 ©2020 McGraw-Hill Education  Check Your Progress List and describe the different types of blood vessels. Describe how each blood vessel contributes to the flow of blood in the body. Explain why the structure of the veins is different from that of the arteries. 13 ©2020 McGraw-Hill Education  The Heart 1 The heart. Located between the lungs. Points toward the left hip. Consists mostly of the myocardium, which is made of cardiac muscle tissue. Cardiac Muscle Physiology Animation: https://youtu.be/IMkHo11reWg 18 ©2020 McGraw-Hill Education  The Heart 2 The heart Surrounded by a sac called the pericardium, which secretes pericardial fluid for lubrication. Internally, the septum divides the heart into right and left sides. Consists of 4 chambers: 2 upper atria and 2 lower ventricles. 20 ©2020 McGraw-Hill Education  The Arteries and Veins Associated with the Heart Access the text alternative for these images 21 ©2020 McGraw-Hill Education  The Heart 3 The heart has: 2 types of valves: semilunar valves and atrioventricular (AV) valves. The AV valves are : Left AV valve—bicuspid, or mitral valve. Right AV valve—tricuspid valve. Semilunar valves: pulmonary valve and aortic valve. 22 ©2020 McGraw-Hill Education  Coronary Circulation: The Heart’s Blood Supply The myocardium needs its own blood supply. Coronary arteries supply it. Coronary veins drain it. Coronary artery disease—blockage in the coronary arteries causes a myocardial infarction (heart attack). 18 ©2020 McGraw-Hill Education  Blood Flow Through the Heart 1 Blood flow through the heart. The superior vena cava and inferior vena cava carry O2-poor, CO2-rich blood from the body to the right atrium. Blood then flows through the right AV (tricuspid) valve into the right ventricle. The right ventricle pumps blood through the pulmonary valve into the pulmonary trunk, which branches into right and left pulmonary arteries. They lead to the lungs. 19 ©2020 McGraw-Hill Education  Blood Flow Through the Heart 2 Blood flow through the heart, continued. The pulmonary veins carry O2-rich, CO2-poor blood from the lungs to the left atrium. Blood then flows through the left AV (bicuspid) valve into the left ventricle. The left ventricle pumps blood through the aortic valve into the aorta. The aorta branches into smaller arteries, which lead to arterioles, then capillaries, venules, veins and back to the vena cavae. 20 ©2020 McGraw-Hill Education  Blood Flow Through the Heart 3 The walls of the left ventricle are thicker than the right ventricle because it must pump blood to the entire body, not just to the lungs. The walls of atria are thinner than ventricles. Flow through the heart: https://youtu.be/7XaftdE_h60 21 ©2020 McGraw-Hill Education  The Heartbeat is Controlled The cardiac cycle. First the atria contract together, then the ventricles, then the heart relaxes. Systole—heart contraction. Diastole—heart relaxation. Occurs 70 times per minute on average. There are two audible sounds: “lub-dub.” Lub: from the closure of the AV valves. Dub: from the closure of the semilunar valves. Murmur: a swishing sound between “lub” and “dub” from regurgitation of blood (leaky valves). 22 ©2020 McGraw-Hill Education  The Stages of the Cardiac Cycle Cardiac Cycle - Systole & Diastole: https://youtu.be/jLTdgrhpDCg Access the text alternative for these images 29 ©2020 McGraw-Hill Education ©Biophoto Associates/Science Source  Internal Control of Heartbeat Internal (intrinsic) conduction system. The SA node in the right atrium initiates the heartbeat by sending out an electrical signal; this causes the atria to contract. SA node is called the pacemaker. This impulse reaches the AV node, also in the right atrium. AV node sends a signal down the AV bundle and Purkinje fibers; this causes ventricular contraction. 30 ©2020 McGraw-Hill Education  An Electrical Signal Pathway Through the Heart Access the text alternative for these images 31 ©2020 McGraw-Hill Education  External Control of Heartbeat External (extrinsic) control of heartbeat. The cardiac control center in the brain increases or decreases the heart rate depending on the body’s needs. Some hormones increase heart rate. 26 ©2020 McGraw-Hill Education  An Electrocardiogram is a Record of the Heartbeat 1 Electrocardiogram (ECG). A recording of the electrical changes in the heart muscle during a cardiac cycle. The atria produce an electrical current, called the P wave, when stimulated by the SA node. QRS complex—wave of electrical current traveling through the ventricles. Signals that the ventricles are about to contract. The recovery of the ventricles is represented as the T wave. 27 ©2020 McGraw-Hill Education  An Electrocardiogram Access the text alternative for these images 34 ©2020 McGraw-Hill Education (a, b): ©Ed Reschke; (c): ©MedicImage/Alamy Stock Photo  An Electrocardiogram Is a Record of the Heartbeat 2 Electrocardiogram (ECG) Detects abnormalities. Eg: ventricular fibrillation— caused by uncoordinated, irregular electrical signals in the ventricles. The heart can’t pump blood; tissues become starved of oxygen. Defibrillation—applying a strong electrical signal to reset the heart; hopefully, the SA node will start firing again. 29 ©2020 McGraw-Hill Education  Check Your Progress Describe the flow of blood through the heart. Explain what causes the “lub” and the “dub” sounds of a heartbeat. Summarize the internal and external controls of the heartbeat. 30 ©2020 McGraw-Hill Education