Biology Skeletal System PDF

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 bo...

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 Muscular System - Part 1 Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023  Learning Outcomes: Identify the three types of muscle tissue and provide a function for each. Describe the general structure of a skeletal muscle. Identify the structures of a muscle fiber. Summarize how activities within the neuromuscular junction control muscle fiber contraction. Explain how the sliding filament model is responsible for muscle contraction. ©2020 McGraw-Hill Education  Overview of the Muscular System 2 Muscular system Functions in: Movement of the entire organism. Movement of materials within the organism. Eg: blood, food. ©2020 McGraw-Hill Education  Types of Muscles Three types of muscle tissue: smooth, cardiac, and skeletal. The cells are called muscle fibers. ©2020 McGraw-Hill Education  Smooth Muscle 1 Fibers are: Shaped like cylinders with pointed ends. Uninucleated. Arranged in parallel lines, forming sheets. Not striated. Located in the walls of hollow internal organs and blood vessels and causes these walls to contract. Contraction is involuntary. ©2020 McGraw-Hill Education  Cardiac Muscle 1 Forms the heart wall. Fibers are: Uninucleated, striated, and tubular. Branched; interlock at intercalated disks. Relaxes completely between contractions, which prevents fatigue. Contraction: Is rhythmic. Occurs without nervous stimulation. Is involuntary. ©2020 McGraw-Hill Education  Skeletal Muscle Fibers are: Tubular, multinucleated, and striated. Make up skeletal muscles, which are attached to the skeleton. Very long; run the length of the muscle. Is voluntarily controlled. ©2020 McGraw-Hill Education  Functions of Skeletal Muscles 1 Functions of skeletal muscles: Support—muscle contraction opposes gravity and allows us to remain upright. Movements of bones and other body structures. Arms, legs, eyes, facial expressions, and breathing. Maintenance of a constant body temperature. Contraction causes ATP (adenosine triphosphate) to break down, releasing heat, which is distributed throughout the body. Protection of the internal organs Muscles pad the bones, and the muscular wall of the abdomen protects internal organs. ©2020 McGraw-Hill Education  Basic Structure of Skeletal Muscles Fascicle—bundle of skeletal muscle fibers. Within a fascicle, muscle fiber each fiber is surrounded by fascicle connective tissue; the fascia dense connective fascicle is also tissue tendon surrounded by connective tissue. ©2020 McGraw-Hill Education  Connecting muscle to bone Fascia—connective tissue muscle fiber that covers muscles and extends to become its fascicle tendon. fascia dense Small, fluid-filled sacs called connective tissue tendon bursae can often be found between tendons and bones. The bursae act as cushions, lubrication. ©2020 McGraw-Hill Education  Skeletal Muscles Work in Pairs 1 For a given movement, the origin of a muscle is the attachment site to the stationary bone, and the insertion is the attachment on the bone that moves. When a muscle contracts, it pulls on the tendons at its insertion and the bone moves. That is, when the biceps brachii contracts, it raises the forearm. 11 ©2020 McGraw-Hill Education  Skeletal Muscles Work in Pairs 2 Skeletal muscles usually function in groups. Agonist (prime mover)—the muscle that does most of the work. Antagonist—the muscle that acts opposite to a prime mover. That is, the biceps and the triceps are antagonistic muscle pair. biceps flexes the forearm, and the triceps extends the forearm. The muscle that is contracting is called the agonist and the muscle that is relaxing, or lengthening is called the antagonist. If both contract at once, there would be no movement. ©2020 McGraw-Hill Education  Check Your Progress State the three types of muscles in the human body and explain where each is found in the body. Summarize the functions of skeletal muscles. Explain how skeletal muscles work together to cause bones to move. ©2020 McGraw-Hill Education  Muscle Fibers and How They Slide 1 Cellular components of a muscle fiber: Sarcolemma—plasma membrane. Sarcoplasm—cytoplasm. Sarcoplasmic reticulum—endoplasmic reticulum. Calcium storage site. T (transverse) tubules—penetrate the cells; come close to portions of the sarcoplasmic reticulum. ©2020 McGraw-Hill Education  Muscle Fibers and How They Slide 2 Cellular components of a muscle fiber, continued: The sarcolemma contains many myofibrils, the contractile parts of muscle fibers. The sarcoplasm also contains glycogen, which provides energy for muscle contraction. The sarcoplasm includes the red pigment myoglobin, which binds oxygen. CHECK POINT ©2020 McGraw-Hill Education  The Structure of a Skeletal Muscle Fiber Cylindrical in shape. Grouped inside this larger cylinder are smaller cylinders called myofibrils. Myofibrils run the entire length of the muscle fiber. Made of smaller cylinders called myofilaments. Two types of myofilaments: Thick myofilaments are made up of myosin. Thin myofilaments are composed of actin. 16 ©2020 McGraw-Hill Education  Anatomy of a Muscle Fiber Table Name Function Sarcolemma The plasma membrane of a muscle fiber. Sarcoplasm The cytoplasm of a muscle fiber that contains the organelles, including myofibrils Myoglobin A red pigment that stores oxygen for muscle contraction T tubule An extension of the sarcolemma that extends into the muscle fiber and conveys impulses that cause Ca2+ to be released from the sarcoplasmic reticulum Sarcoplasmic The smooth endoplasmic reticulum (ER) of a muscle fiber that reticulum stores Ca2+ Myofibril A bundle of myofilaments that contracts Myofilament An actin or a myosin filament, whose structure and functions account for muscle striations and contractions ©2020 McGraw-Hill Education  Myofibrils and Sarcomeres 3 Myofibrils are further divided into sarcomeres. Sarcomeres extend between two dark vertical lines called Z lines. I band—light colored; made of only thin myofilaments. A band—made of overlapping thin and thick myofilaments. Centered within the A band is a vertical H band, which contains only thick myofilaments. ©2020 McGraw-Hill Education  Thick and Thin Myofilaments 1 Thick filaments. Thin filaments. Composed of the Made of two protein myosin. intertwining strands Each myosin molecule is of the protein shaped like a golf club, actin, with with the straight portion of the molecule tropomyosin, and ending in a globular troponin. head, or cross-bridge. ©2020 McGraw-Hill Education  Sliding Filament Model 1 Sliding filament model: the muscle fiber contracts as the sarcomeres shorten. ATP supplies the energy for muscle contraction. Note that when the sarcomere contracts, the filaments themselves remain the same length. The thin filaments slide past the thick filaments. The I band shortens, the Z lines move inward, and the H band almost disappears. ©2020 McGraw-Hill Education  Muscle Fiber Contraction 1 Motor neuron—a type of nervous system cell that stimulates muscle fibers to contract. Nerve—group of neurons. Axon—the part of a neuron that stimulates a muscle fiber. Branches, so can stimulate several muscle fibers. ©2020 McGraw-Hill Education Motor Neurons and Skeletal Muscle Fibers Join Neuromuscular Junctions ©2020 McGraw-Hill Education  Muscle Fiber Contraction 2 Neuromuscular junction. Where an axon terminal (end of an axon) comes near the sarcolemma. Synaptic cleft—the space that separates the two. Axon terminals contain synaptic vesicles filled with the neurotransmitter acetylcholine (ACh). When nerve signals traveling down the axon arrive at an axon terminal, synaptic vesicles release ACh into the synaptic cleft. ©2020 McGraw-Hill Education Motor Neurons and Skeletal Muscle Fibers Join Neuromuscular Junctions ACh diffuses across the cleft and binds to receptors in the sarcolemma. This generates electrical signals that spread across the sarcolemma and down the T tubules. This causes calcium to be released from the sarcoplasmic reticulum. 24 ©2020 McGraw-Hill Education  More Muscle Fiber Contraction When Ca2+ is released from the sarcoplasmic reticulum, it binds to troponin. The tropomyosin threads move, exposing myosin-binding sites. The Role of Calcium Ions and ATP During Muscular Contraction Threads of tropomyosin wind around the strands of actin, covering binding sites for myosin. Troponin occurs at intervals along the threads. 25 ©2020 McGraw-Hill Education  Steps of the Sliding Filament Theory 1 The myosin heads have ATP-binding sites. At this site, ATP is split to form ADP and P. Myosin heads attach to actin. Form temporary bonds called cross-bridges. ADP and P are then released and the myosin heads bend. This is the power stroke that pulls the actin filament toward the center of the sarcomere. 26 ©2020 McGraw-Hill Education  Steps of the Sliding Filament Theory 2 The binding of ATP to myosin heads breaks the cross-bridges. Myosin detaches from actin. The cycle begins again and myosin reattaches farther along the actin filament. The cycle recurs over and over, shortening the sarcomere (and therefore the muscle). The continuous sliding action of the myosin and actin filaments is called the ratchet mechanism. ATP 27 ©2020 McGraw-Hill Education  Steps of the Sliding Filament Theory 2 ATP and Ca2+ are important for muscle contraction  Check Your Progress Explain the role of the myofibril in a muscle fiber. Describe the role of both ATP and calcium ions in muscle contraction. CHECK POINT 29 ©2020 McGraw-Hill Education Muscular System - Part 2 Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023 Learning Outcomes: Summarize how muscle cells produce ATP for muscle contraction. 2 ©2020 McGraw-Hill Education  Energy for Muscle Contraction Muscles have four different sources of energy: Two are stored in muscle (glycogen, triglycerides) and two are acquired from blood (glucose, fatty acids). Which of these are used depends on exercise intensity and duration. As time of exercise increases, use of muscle energy stores decreases and use of energy sources from the blood increases. 3 ©2020 McGraw-Hill Education  The Sources of Energy for Muscle Contraction Access the text alternative for these images 4 ©2020 McGraw-Hill Education  Sources of ATP for Muscle Contraction Muscle cells store limited amounts of ATP. Once it is used up, they have three ways to produce more ATP: The creatine phosphate (CP) pathway. Fermentation. Cellular respiration. Mitochondria uses oxygen, so is aerobic; neither the CP pathway nor fermentation requires oxygen (are anaerobic). 5 ©2020 McGraw-Hill Education  The Three Pathways by Which Muscle Cells Produce the ATP Energy Needed for Contraction Access the text alternative for these images 6 ©2020 McGraw-Hill Education  The Creatine Phosphate Pathway 1 The creatine phosphate pathway—the simplest and fastest way for muscle to make ATP 7 ©2020 McGraw-Hill Education  The Creatine Phosphate Pathway 2 Creatine phosphate is formed only when a muscle cell is resting, and only a limited amount is stored. Creatine phosphate-derived ATP powers the first few seconds of muscle contraction The CP pathway is used at the beginning of exercise. Creatine phosphate can only provide approximately 15 seconds worth of energy, at which point another energy source has to be used. 8 ©2020 McGraw-Hill Education  Fermentation 1 The anaerobic processes of glycolysis and fermentation produce two ATPs from the breakdown of glucose to lactate. Hormones signal cells to break down glycogen, making glucose available as an energy source. Fermentation, like the CP pathway, is fast-acting, but results in the buildup of lactate. Lactate produces short-term muscle aches and fatigue. 9 ©2020 McGraw-Hill Education  Fermentation 2 Oxygen debt—heavy breathing following strenuous exercise is required to complete the metabolism of lactate and restore cells to their original energy state. 10 ©2020 McGraw-Hill Education  Cellular Respiration Cellular respiration—the slowest of all three mechanisms used to produce ATP, but the most efficient. Occurs in the mitochondria. Myoglobin—a protein in muscle cells that delivers oxygen directly to the mitochondria. Can use glucose from stored glycogen, glucose in the blood, and fatty acids. 11 ©2020 McGraw-Hill Education  Check Your Progress Summarize how the CP pathway, fermentation, and cellular respiration produce ATP for muscle contraction. 12 ©2020 McGraw-Hill Education Reproductive System- Part 1 Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023  Human Life Cycle 1 Learning Outcomes: Describe the human life cycle and explain the role of mitosis and meiosis in this cycle. Describe functions for each male and female reproductive system organ. Describe the location and stages of spermatogenesis. Summarize how hormones regulate the male reproductive system. 2 ©2020 McGraw-Hill Education  Human Life Cycle 2 Reproductive system—produces gametes (eggs, sperm). Females also protect and nourish the developing fetus until birth. 3 ©2020 McGraw-Hill Education  Functions of the Reproductive Organs 1 The reproductive organs, or genitals, have the following functions: Males produce sperm within testes, and females produce eggs within ovaries. Males transport sperm in ducts; females transport eggs in uterine tubes to the uterus. The uterus allows the fertilized egg to develop within the body. After birth, the breast provides nourishment. The testes and ovaries produce sex hormones. Bring about masculinization or feminization. 4 ©2020 McGraw-Hill Education  Puberty The time period during which a child becomes a sexually competent adult. Sexual maturity typically occurs between the ages of 10 and 14 in girls and 12 and 16 in boys. At the completion of puberty, the individual is capable of producing children. 5 ©2020 McGraw-Hill Education  Mitosis and Meiosis 1 DNA (Deoxyribonucleic acid)—genetic instructions. Distributed among 46 chromosomes within the nucleus of most body cells. 23 pairs; each pair contains one from both parents. 6 ©2020 McGraw-Hill Education  Mitosis and Meiosis 2 During most of the life cycle, cells divide by mitosis. Mitosis is duplication division; each of the cells that exit mitosis has the same 46 chromosomes. Cells produce exact copies of themselves. Mitosis is used for growth and repair of damaged tissues. 7 ©2020 McGraw-Hill Education  Mitosis and Meiosis 3 Meiosis—cell division for the purposes of reproduction. Takes place only in the testes (during sperm production) and ovaries (during egg production). 8 ©2020 McGraw-Hill Education  More Mitosis and Meiosis 1 Is also called reduction division. Chromosome number is reduced from 46 (diploid or 2n) to 23 (haploid or n). Requires two successive divisions, called meiosis I and meiosis II. Introduces genetic variation. 9 ©2020 McGraw-Hill Education  More Mitosis and Meiosis 2 Following meiosis, the haploid cells develop into either sperm (males) or eggs (females). Sperm are much smaller than eggs. Zygote—formed by fusing the egg and sperm. Because they each have 23 chromosomes, the zygote has 46. 10 ©2020 McGraw-Hill Education  Check Your Progress Compare the functions of the reproductive system in males and females. Contrast the two types of cell division in the human life cycle. Explain the location of meiosis in males and females. 11 ©2020 McGraw-Hill Education  Male Reproductive Organs Male Reproductive Organs. Organ Function Testes Produce sperm and sex hormones Ducts where sperm mature and some Epididymides sperm are stored Vasa deferentia Conduct and store sperm Seminal vesicles Contribute nutrients to seminal fluid. Prostate gland Secrets fluid that nourishes and protects sperm Urethra Conducts sperm 12 ©2020 McGraw-Hill Education  Semen Semen (seminal fluid). Slightly basic pH (about 7.5). Contains the sugar fructose, which serves as an energy source. Contains prostaglandins, which cause the uterus to contract to propel the sperm toward the egg. 13 ©2020 McGraw-Hill Education  Seminiferous Tubules 1 Seminiferous tubules. Testes have compartments called lobules, each of which contains seminiferous tubules. Spermatogenesis—the production of sperm; occurs in the seminiferous tubules. Spermatogonia divide to produce primary spermatocytes (2n), which undergo meiosis I to produce secondary spermatocytes (n). These undergo meiosis II to produce four spermatids (also n, or 23 chromosomes). 14 ©2020 McGraw-Hill Education  Spermatogenesis Produces Sperm Cells Access the text alternative for these images 15 ©2020 McGraw-Hill Education  Seminiferous Tubules 2 Spermatogenesis, continued. Spermatids then develop into sperm. Sertoli cells—support, nourish, and regulate the process of spermatogenesis. Takes 74 days for development from spermatogonia to sperm. CHECK POINT 32 ©2020 McGraw-Hill Education  Spermatogenesis Produces Sperm Cells Access the text alternative for these images 33 ©2020 McGraw-Hill Education  Seminiferous Tubules 3 Spermatogenesis, concluded. Sperm (spermatozoa)—have three parts: head, middle piece, and tail. Mitochondria in the middle piece provide energy for the movement of the tail, which is a flagellum. The head contains a nucleus covered by the acrosome, which contains enzymes needed to penetrate the egg. 18 ©2020 McGraw-Hill Education  Spermatogenesis Produces Sperm Cells 19 ©2020 McGraw-Hill Education  Interstitial Cells Interstitial Cells. Produce the male sex hormones (androgens). The most important of the androgens is testosterone. Lie between the seminiferous tubules. 20 ©2020 McGraw-Hill Education  Hormonal Regulation in Males 1 Hypothalamus secretes gonadotropin-releasing hormone (GnRH), which stimulates the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). In males, FSH promotes the production of sperm. LH stimulates the production of testosterone. Controlled by negative feedback; this maintains the fairly constant production of sperm and testosterone. 21 ©2020 McGraw-Hill Education  The Hormones that Control the Production of Sperm and Testosterone by the Testes Access the text alternative for these images 22 ©2020 McGraw-Hill Education  Hormonal Regulation in Males 2 Testosterone—main sex hormone in males. Essential for normal development and functioning of male sex organs. Brings about and maintains the male secondary sex characteristics that develop at puberty. Males are generally taller than females. Broad shoulders, longer legs relative to trunk length. Deeper voices due to a larger larynx with longer vocal cords. Hair growth on the face, chest, other regions. Greater muscular development. 23 ©2020 McGraw-Hill Education  Check Your Progress Describe the process of spermatogenesis. Explain the importance of testosterone to the male reproductive system. 24 ©2020 McGraw-Hill Education  Female Reproductive System 2 Ovaries—the female gonads. one on each side of the upper pelvic cavity. Produce eggs, also called ova (singular, ovum). Produce the female sex hormones estrogen and progesterone. 25 ©2020 McGraw-Hill Education  The Genital Tract 1 Uterine tubes (oviducts, fallopian tubes) extend from the uterus to the ovaries. Are not attached to the ovaries; they have fingerlike projections called fimbriae. After ovulation, the fimbriae sweep the egg into a uterine tube. In the uterine tube, the egg is propelled by ciliary movement toward the uterus. 26 ©2020 McGraw-Hill Education  The Genital Tract 2 An egg lives approximately 6 to 24 hours Fertilization usually takes place in the uterine tube. An embryo implants after several days. Embeds in the uterine lining. 27 ©2020 McGraw-Hill Education  The Genital Tract 3 Uterus—. thick-walled, muscular organ Endometrium—the lining of the uterus. Supplies nutrients needed for embryonic and fetal development. 28 ©2020 McGraw-Hill Education Female Reproductive Organs Organ Function Ovaries Produce eggs and sex hormones Uterine tubes Conduct eggs; location of fertilization Uterus Houses developing fetus Cervix Contains opening to uterus Cancer of the cervix is a common form of cancer in women. Pap test—the removal of a few cells from the cervix for microscopic examination. Hysterectomy—surgical removal of the uterus. Ovariohysterectomy—removal of ovaries and uterus. ©2020 McGraw-Hill Education CHECK POINT 29 Reproductive System- Part 2 Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023  Learning Outcomes: List the stages of the ovarian cycle and explain what is occurring in each stage. Describe the process of oogenesis. Summarize how estrogen and progesterone influence the ovarian cycle. The Effect of Birth Control Pills on the Ovarian Cycle. 2 ©2020 McGraw-Hill Education  Ovarian Cycle: Nonpregnant 1 Oocyte—immature egg; contained within a follicle. Females are born with 2 million follicles, but have only 300,000—400,000 by puberty. Only 400 ever mature; a female produces only one egg per month during her reproductive years. As the follicle matures during the ovarian cycle, it changes from a primary to a secondary to a vesicular (Graafian) follicle. 3 ©2020 McGraw-Hill Education  The Ovarian Cycle Access the text alternative for these images 61 ©2020 McGraw-Hill Education (photo): ©Ed Reschke  Ovarian Cycle: Nonpregnant 2 Oocyte, continued. Primary follicle—epithelial cells surround a primary oocyte. Secondary follicle—follicular fluid surrounds the secondary oocyte. Vesicular follicle—the fluid-filled cavity enlarges to the point that the follicle wall balloons out on the surface of the ovary. 5 ©2020 McGraw-Hill Education  Oogenesis 1 Steps of oogenesis (production of an oocyte): A primary oocyte undergoes meiosis I; the two resulting cells are haploid. One of these cells is called a polar body; its function is simply to hold discarded chromosomes. The secondary oocyte undergoes meiosis II, but only if it is first fertilized by a sperm cell. If it remains unfertilized, it never completes meiosis and dies shortly after being released from the ovary. 6 ©2020 McGraw-Hill Education  Oogenesis Produces Egg Cells Access the text alternative for these images 7 ©2020 McGraw-Hill Education  Oogenesis 2 Steps of oogenesis, continued: Ovulation—the vesicular follicle bursts, releasing the oocyte. The vesicular follicle then develops into a corpus luteum, a glandlike structure. If the egg is not fertilized, the corpus luteum disintegrates. 8 ©2020 McGraw-Hill Education  Oogenesis 3 Steps of oogenesis, concluded: A primary follicle produces estrogen, and a secondary follicle produces estrogen and some progesterone The corpus luteum produces progesterone and some estrogen. 9 ©2020 McGraw-Hill Education  Phases of the Ovarian Cycle 1 Like in males, the hypothalamus secretes GnRH. GnRH stimulates the anterior pituitary to produce FSH and LH; these hormones control the ovarian cycle. 10 ©2020 McGraw-Hill Education  The Hormones that Control the Production of Estrogen and Progesterone by the Ovaries Access the text alternative for these images 11 ©2020 McGraw-Hill Education  Phases of the Ovarian Cycle 2 Follicular phase—the first half of the cycle. FSH promotes the development of primary follicles, which primarily secrete estrogen. As estrogen rises, it exerts negative feedback control over the anterior pituitary secretion of FSH, ending the follicular phase. A surge of LH is released from the anterior pituitary, triggering ovulation on day 14 of a 28-day cycle. 12 ©2020 McGraw-Hill Education  Female Hormone Levels During the Ovarian and Uterine Cycles Access the text alternative for these images 13 ©2020 McGraw-Hill Education  Phases of the Ovarian Cycle 3 Luteal phase—LH promotes the development of the corpus luteum, which secretes high levels of progesterone and some estrogen. If pregnancy does not occur, it regresses and a new cycle begins. 14 ©2020 McGraw-Hill Education  Estrogen and Progesterone 1 Estrogen and progesterone. Responsible for the secondary sex characteristics: Terminal hair after puberty. Greater fat accumulation under the skin. Both estrogen and progesterone are also required for breast development. Prolactin is involved in milk production after pregnancy. CHECK POINT 15 ©2020 McGraw-Hill Education  Estrogen and Progesterone 3 Menopause—when the ovarian cycle ceases. Usually between ages 45 and 55. The ovaries no longer respond to gonadotropic hormones, and they no longer secrete estrogen or progesterone. At the onset of menopause, menstruation becomes irregular, but it is not complete until menstruation is absent for 1 year. 16 ©2020 McGraw-Hill Education  Uterine Cycle: Nonpregnant 1 Uterine cycle—a cyclical series of events caused by estrogen and progesterone. Twenty-eight-day cycles are divided as follows: Days 1 to 5: menstruation—low levels of estrogen and progesterone cause the endometrium to disintegrate and its blood vessels to rupture. Menses—the flow of blood and tissues out of the vagina. 17 ©2020 McGraw-Hill Education  Uterine Cycle: Nonpregnant 2 Uterine cycle, continued. Days 6 to 13: proliferative phase—increased production of estrogen by a new follicle causes the endometrium to thicken and become glandular. On day 14—ovulation. 18 ©2020 McGraw-Hill Education  Uterine Cycle: Nonpregnant 3 Uterine cycle, concluded. Days 15 to 28: secretory phase—increased production of progesterone by the corpus luteum causes the endometrium thicken. Also causes the uterine glands to mature and produce a thick secretion. The endometrium is now prepared to receive the developing embryo; if this does not occur, the corpus luteum regresses. The resulting low level of progesterone causes menstruation. 19 ©2020 McGraw-Hill Education  Ovarian and Uterine Cycles: Nonpregnant Ovarian and Uterine Cycles: Nonpregnant. Ovarian Cycle Events Uterine Cycle Events Follicular phase—days FSH secretion Menstruation—days Endometrium 1 to 13 begins. 1 to 5 breaks down. Follicle maturation Proliferative Endometrium occurs. phase—days 6 to 13 rebuilds. Estrogen secretion is prominent. Ovulation-day 141 LH spike occurs. Luteal phase-days 15 to LH secretion Secretory phase— Endometrium 28 continues. days 15 to 28 thickens, and glands Corpus luteum are secretory. forms. Progesterone secretion is prominent. 1 assuming a 28-day cycle. 20 ©2020 McGraw-Hill Education  Fertilization and Pregnancy 1 Only one sperm is needed to fertilize the egg, which is then called a zygote. As the zygote travels down the uterine tube to the uterus, it begins mitosis. Once it is made of many cells, it is called an embryo. The endometrium is now prepared to receive the developing embryo. 21 ©2020 McGraw-Hill Education  Fertilization and Pregnancy 2 The embryo implants in the endometrial lining several days following fertilization. Implantation signals the beginning of a pregnancy. An abortion may be spontaneous (referred to as a miscarriage) or induced. Both end with loss of the embryo or fetus. 22 ©2020 McGraw-Hill Education  Placenta 1 Placenta—sustains the developing embryo. Originates from both maternal and fetal tissues. Where exchange between fetal and maternal blood occurs. Produces human chorionic gonadotropin (HCG)— maintains the corpus luteum. A pregnancy test detects HCG in the blood or urine. 23 ©2020 McGraw-Hill Education  Placenta 2 Placenta, continued. Rising amounts of HCG stimulate the corpus luteum to produce increasing amounts of progesterone. This progesterone shuts down the hypothalamus and anterior pituitary, so no new follicles begin to develop. The progesterone maintains the uterine lining where the embryo now resides, preventing menstruation. 24 ©2020 McGraw-Hill Education  The Effect of Pregnancy on the Corpus Luteum and Endometrium 25 ©2020 McGraw-Hill Education  Placenta 3 Placenta, concluded. Eventually, the placenta produces progesterone and some estrogen. So the corpus luteum is no longer needed and it regresses. CHECK POINT 26 ©2020 McGraw-Hill Education  Birth Control Pills Birth control pills to prevent pregnancy usually involve taking active pills (contain estrogen and progesterone) for 21 days, then inactive pills (do not contain them) for 7 days. The uterine lining builds up while the active pills are being taken. Progesterone decreases after the last active pills are taken, causing menstruation. 27 ©2020 McGraw-Hill Education  The Effect of Birth Control Pills on the Ovarian Cycle 28 ©2020 McGraw-Hill Education  Check Your Progress Summarize the roles of estrogen and progesterone in the ovarian and uterine cycles. CHECK POINT 29 ©2020 McGraw-Hill Education Human genetics- Part 1 Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023  Learning Outcomes: Distinguish between a chromosome and chromatin. Explain the purpose of a karyotype. List the stages of the cell cycle and state the purpose of each. Describe the purpose of the checkpoints in the cell cycle. Distinguish between mitosis and cytokinesis. 2 ©2020 McGraw-Hill Education  Chromosomes 1 The nucleus holds all the genetic material to direct all the functions in the body. Chromosomes—made of DNA. The instructions in each chromosome are contained within genes, which in turn are composed of DNA. 3 ©2020 McGraw-Hill Education  Chromosomes 2 Chromosomes, continued. Contain proteins that assist in the organizational structure. Collectively, the DNA and proteins are called chromatin. Humans have 46 chromosomes, in 23 pairs. 22 of these pairs are called autosomes—found in both males and females. One pair is called the sex chromosomes, because they contain genes that control gender. 4 ©2020 McGraw-Hill Education  Chromosomes 3 Males have the sex chromosomes X and Y, and females have two X chromosomes. The Y chromosome contains the SRY gene that causes testes to develop. 5 ©2020 McGraw-Hill Education  A Karyotype 1 A display of the chromosomes present in a cell. When a cell divides, chromatin condenses to form chromosomes. Staining causes the Karyotype chromosomes to have dark and light cross-bands of varying widths, and a computer uses these, in addition to size and shape, to pair up the chromosomes. 6 ©2020 McGraw-Hill Education  A Karyotype of Human Chromosomes Access the text alternative for these images 7 ©2020 McGraw-Hill Education (photo): ©CNRI/SPL/Science Source  A Karyotype 2 Mitosis—cell division that begins when the fertilized egg starts dividing. Ensures that every cell is diploid (has 46 chromosomes). In dividing cells, each chromosome is composed of two identical parts called sister chromatids. These are said to be replicated or duplicated chromosomes because the two sister chromatids contain the same genes. 8 ©2020 McGraw-Hill Education  A Karyotype 3 Centromere—holds the chromatids together until a certain phase of mitosis, when the centromere splits. Daughter chromosomes separate, the new cell gets one of each type (a full set of chromosomes). 9 ©2020 McGraw-Hill Education  Check Your Progress Explain the purpose of chromosomes in a cell. Describe how a karyotype can be used to determine the number of chromosomes in a cell. Explain why sister chromatids are genetically the same. 10 ©2020 McGraw-Hill Education  The Cell Cycle 2 Cell cycle—has two parts: interphase and cell division. When a cell is not undergoing division, the chromatin appears to be a tangled mass of thin threads. 11 ©2020 McGraw-Hill Education  Interphase 1 Most of the cell cycle is spent in interphase. Organelles carry on their usual functions. The cell gets ready to divide: it grows larger, the number of organelles doubles, and the amount of chromatin doubles (DNA replication). Divided into three main stages: G1, S, G2. 12 ©2020 McGraw-Hill Education  Stages of the Cell Cycle Access the text alternative for these images 13 ©2020 McGraw-Hill Education  Interphase 2 Phases of interphase: G1 stage—the cell performs its normal function. Also doubles its organelles and accumulates the materials needed for DNA synthesis. S stage—DNA replication. After the S stage, each chromosome consists of two identical sister chromatids. G2 stage—synthesizes the proteins needed for cell division. 14 ©2020 McGraw-Hill Education  Interphase 3 The amount of time the cell spends in interphase varies widely. Some cells, such as nerve and muscle cells, typically do not complete the cell cycle and are permanently arrested in G1. they won’t ever continue to the S and G2phases, they are instead said to be in a G0 stage. Embryonic cells spend very little time in G1 and complete the cell cycle in a few hours. 15 ©2020 McGraw-Hill Education  Mitosis and Cytokinesis 1 Following interphase is cell division. Cell division has two stages: M (for “mitosis”) stage and cytokinesis. Mitosis is a type of nuclear division. Also referred to as duplication division since each new nucleus contains the same number and type of chromosomes as the former cell. Cytokinesis—division of the cytoplasm. 16 ©2020 McGraw-Hill Education  Mitosis and Cytokinesis 2 The cell cycle occurs continuously in certain tissues. Mitosis is balanced by the process of apoptosis, or programmed cell death. Apoptosis occurs when cells are no longer needed or have become excessively damaged. 17 ©2020 McGraw-Hill Education  Cell Cycle Control The cell cycle is controlled by checkpoints, which delay it until certain conditions are met. That is, G1 checkpoint, G2 checkpoint, and the mitotic checkpoint. The cell cycle may also be controlled by external factors, such as hormones and growth factors. Failure of the cell cycle control mechanisms may result in unrestricted cell growth, or cancer. 18 ©2020 McGraw-Hill Education  Control of the Cell Cycle Access the text alternative for these images 19 ©2020 McGraw-Hill Education  𝐆𝟏Checkpoint 1 G1 checkpoint—if the cell cycle passes this checkpoint, the cell is committed to divide. If the cell does not pass this checkpoint, it can enter G0, where it performs normal functions but does not divide. Proper growth signals, such as growth factors, must be present for a cell to pass the G1 checkpoint. 20 ©2020 McGraw-Hill Education  𝐆𝟏Checkpoint 2 G1 checkpoint, continued. The integrity of the DNA is also checked. If DNA is damaged, proteins such as p53 can stop the cycle at this checkpoint and place the cell in G0. If the DNA can be repaired, it may reenter the cell cycle; if not, it may undergo apoptosis. 21 ©2020 McGraw-Hill Education  𝐆2Checkpoint G2 checkpoint The cell cycle halts here until the cell verifies that DNA has replicated. Prevents the initiation of the M stage unless the chromosomes are duplicated. If DNA is damaged, arresting the cell cycle allows time for the damage to be repaired so that it is not passed on to daughter cells. 22 ©2020 McGraw-Hill Education  Mitotic Checkpoints Mitotic checkpoint—occurs between metaphase and anaphase to make sure the chromosomes are properly attached to the spindle so can be distributed accurately to the daughter cells. 23 ©2020 McGraw-Hill Education  External Control of the Cell Cycle External control. An external signal, such as a hormone or growth factor, can stimulate a cell to divide. It binds to a receptor in the plasma membrane of a target cell. The signal is then relayed from the receptor to proteins inside the cell. The proteins form a pathway called the signal transduction pathway; they pass the signal from one to the next. 25 ©2020 McGraw-Hill Education  External Controls of the Cell Cycle Access the text alternative for these images 26 ©2020 McGraw-Hill Education  External Control 2 External control, continued. The last signal of the signal transduction pathway activates genes in the nucleus. The expression of these genes may stimulate or inhibit the cell cycle. Genes called proto-oncogenes stimulate the cell cycle, and genes called tumor suppressor genes inhibit the cell cycle. 27 ©2020 McGraw-Hill Education  Check Your Progress Describe the cell cycle, and list the locations of each phase and checkpoint. Explain the purpose of the S phase in the cell cycle. Explain how checkpoints help protect the cell against unregulated cell growth. Summarize why external controls may be necessary to regulate the cell cycle. 28 ©2020 McGraw-Hill Education Human genetics- Part II Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023  Learning Outcomes: Explain the purpose of mitosis. Explain the events that occur in each stage of mitosis. State the purpose of cytokinesis. List the stages of meiosis and describe what occurs in each stage. Explain how meiosis increases genetic variation. Differentiate between spermatogenesis and oogenesis with regard to occurrence and the number of functional gametes produced by each process. 2 ©2020 McGraw-Hill Education  Mitosis 2 Mitosis. Creates new cells in the developing embryo, fetus, and child. Responsible for replacement of cells in adults. During mitosis, the cell that divides is called the parent cell, and the new cells are called daughter cells. Referred to as duplication division since the two daughter cells are genetically identical to the parent cell. 3 ©2020 McGraw-Hill Education  The Importance of Mitosis (fresh wound): ©Scott Camazine/ Science Source; (healing wound): ©Edward Kinsman/Science Source 4 ©2020 McGraw-Hill Education  Overview of Mitosis DNA Replication and Division DNA is replicated during the S phase of interphase. At the end of the S phase, each chromosome contains two identical parts, called sister chromatids, held together at a centromere. Access the text alternative for these images 5 ©2020 McGraw-Hill Education  Overview of Mitosis 2 As mitosis begins, the chromosomes condense Following separation during mitosis, each chromatid is called a chromosome. Each daughter cell gets a complete set of chromosomes and is diploid (2n). The daughter cells are genetically identical to each other and to the parent cell. 6 ©2020 McGraw-Hill Education  The Mitotic Spindle 1 Centrosome—the microtubule organizing center of the cell. After they duplicate, they separate and form the poles of the mitotic spindle, where they assemble the microtubules that make up the spindle fibers. The chromosomes are attached to the spindle fibers at their centromeres. Aster—an array of microtubules. Each centrosome contains a pair of centrioles, which consist of short cylinders of microtubules. 7 ©2020 McGraw-Hill Education  Phases of Mitosis Mitosis is divided into phases: prophase, prometaphase, metaphase, anaphase, and telophase. The stages are continuous; one stage flows from the other with no noticeable interruption. 9 ©2020 McGraw-Hill Education  Prophase The centrosomes have duplicated, and move toward opposite ends of the nucleus. Spindle fibers appear. The nuclear envelope begins to fragment. The nucleolus disappears. The chromosomes condense (are now visible). Each is composed of two sister chromatids held together at a centromere. 10 ©2020 McGraw-Hill Education  Stages of Mitosis Access the text alternative for these images 39 ©2020 McGraw-Hill Education (photos) (early prophase, prophase, metaphase, anaphase, telophase): ©Ed Reschke; (prometaphase): ©Michael Abbey/Science Source  Prometaphase Prometaphase. The spindle fibers attach to the centromeres as the chromosomes continue to shorten and thicken. Chromosomes are randomly placed in the nucleus. Metaphase. The metaphase plate is a plane perpendicular to the axis of the spindle and equidistant from the poles. The chromosomes, attached to spindle fibers, line up at the metaphase plate. 12 ©2020 McGraw-Hill Education  Stages of Mitosis Access the text alternative for these images 42 ©2020 McGraw-Hill Education (photos) (early prophase, prophase, metaphase, anaphase, telophase): ©Ed Reschke; (prometaphase): ©Michael Abbey/Science Source  Anaphase Anaphase—centromeres divide. The sister chromatids separate and move toward opposite poles of the spindle. Sister chromatids are now called chromosomes. 14 ©2020 McGraw-Hill Education  Telophase Telophase. Begins when chromosomes arrive at the poles. Chromosomes become indistinct chromatin again. The spindle disappears. The nuclear envelope reappears. The nucleolus reappears. Characterized by the presence of two daughter nuclei. 15 ©2020 McGraw-Hill Education  Cytokinesis Cytokinesis—division of the cytoplasm and organelles. An indentation called a cleavage furrow passes around the circumference of the cell. Actin filaments form a contractile ring; as the ring becomes smaller, the cleavage furrow pinches the cell in half. 16 ©2020 McGraw-Hill Education  Check Your Progress Explain how the chromosome number of the daughter cell compares with the chromosome number of the parent cell following mitosis. List the phases of mitosis and explain what happens during each phase. Describe how the cytoplasm is divided between the daughter cells following mitosis. 17 ©2020 McGraw-Hill Education  Meiosis 2 Meiosis—reduction division. Has two consecutive cell divisions without an interphase in between. Results in four daughter cells, each of which has one of each type of chromosome. The parent cell is diploid (2n); the daughter cells are haploid (n). Introduces genetic variation; each of the daughter cells is genetically different from the parent cell. Possesses new combinations of the genetic material. 18 ©2020 McGraw-Hill Education  Overview of Meiosis At the start of meiosis, the parent cell is diploid (2n), and the chromosomes occur in pairs. The members of a pair are called homologous chromosomes. They look alike and carry genes for the same traits. 19 ©2020 McGraw-Hill Education  Meiosis I Meiosis I and meiosis II—the two cell divisions of meiosis. Prior to meiosis I, DNA has been replicated. Synapsis—homologous chromosomes come together and line up side by side during meiosis I. Keeps the four chromatids close during the first two phases of meiosis I. DNA does not replicate during interkinesis, the time between meiosis I and meiosis II. 20 ©2020 McGraw-Hill Education  Meiosis II During meiosis II, the centromeres divide. The sister chromatids separate and move toward opposite poles of the spindle. Sister chromatids are now called chromosomes. The daughter cells mature into gametes (sperm and egg). Fertilization restores the diploid number of chromosomes in the zygote. 21 ©2020 McGraw-Hill Education  Meiosis I Meiosis II Access the text alternative for these images 22 ©2020 McGraw-Hill Education  Meiosis and Genetic Variation Meiosis ensures that offspring will be diploid and have a combination of genetic characteristics different from that of either parent. Both meiosis I and meiosis II have the same four stages of nuclear division as mitosis. 23 ©2020 McGraw-Hill Education  Prophase I Synapsis occurs; homologous chromosomes line up side by side. Crossing-over—an exchange of genetic material between the nonsister chromatids of the homologous pair. Produces chromatids that are no longer identical. 24 ©2020 McGraw-Hill Education  Metaphase I During metaphase I, the homologous pairs align independently at the equator. 25 ©2020 McGraw-Hill Education  Spermatogenesis and Oogenesis Meiosis is a part of spermatogenesis, the production of sperm in males, and oogenesis, the production of eggs in females. Following meiosis, the daughter cells mature to become the gametes. Is continual in the testes starting at puberty. 300,000 sperm are made per minute; over 400 million per day. Primary spermatocytes—diploid (2n). Divide during meiosis I to form two secondary spermatocytes, which are haploid (n). 26 ©2020 McGraw-Hill Education  Spermatogenesis 2 Secondary spermatocytes divide during meiosis II to produce four spermatids. The chromosomes in secondary spermatocytes are duplicated and consist of two chromatids, whereas those in spermatids consist of only one. Spermatids mature into sperm (spermatozoa). All four daughter cells become sperm. 27 ©2020 McGraw-Hill Education  Oogenesis 1 Ovaries contain many immature follicles, which contain a primary oocyte arrested in prophase I. The primary oocyte, which is diploid (2n), divides during meiosis I into two haploid cells: Begins meiosis II but stops at metaphase II; doesn’t complete it unless a sperm fertilizes it. First polar body—holds discarded chromosomes. 28 ©2020 McGraw-Hill Education  Oogenesis 2 The secondary oocyte (egg) leaves the ovary during ovulation and enters a uterine tube. If it is fertilized, the oocyte is activated to complete the second meiotic division. Following meiosis II, there is one egg and two or possibly three polar bodies. The polar bodies disintegrate, which is a way to discard unnecessary chromosomes while keeping most of the cytoplasm in the egg. 29 ©2020 McGraw-Hill Education  Significance of Meiosis Significance of meiosis. One function is to keep the chromosome number constant from generation to generation. Another is that it results in genetic recombination. Genetic recombination ensures that offspring will be genetically different from each other and their parents. Results from crossing-over and independent alignment of chromosomes. Generates the diversity needed to survive in changing conditions. 30 ©2020 McGraw-Hill Education Human genetics- Part III Nermin Eissa, Ph.D. College of Health Sciences Abu Dhabi University Fall-2023  Learning Outcomes: Distinguish between meiosis and mitosis with regard to the number of divisions and the number and chromosome content of the resulting cells. Contrast the events of meiosis I and meiosis II with the events of mitosis. Explain how nondisjunction produces monosomy and trisomy chromosome conditions. Describe the causes and consequences of trisomy 21. Describe the effects of deletions, duplications, inversions, and translocations on chromosome structure. 2 ©2020 McGraw-Hill Education  Comparison of Meiosis and Mitosis 2 Comparison of meiosis and mitosis: DNA replication takes place only once prior to both meiosis and mitosis. Meiosis requires two nuclear divisions, mitosis only one. Meiosis produces four daughter cells, mitosis two. Daughter cells of meiosis are haploid (n); of mitosis, diploid. 3 ©2020 McGraw-Hill Education  A Comparison of Meiosis and Mitosis Access the text alternative for these images 4 ©2020 McGraw-Hill Education  Comparison of Meiosis and Mitosis 3 The daughter cells of meiosis are not genetically identical to each other or to the parent cell; the daughter cells of mitosis are. The specific differences between these nuclear divisions can be categorized according to occurrence and process. 5 ©2020 McGraw-Hill Education  Occurrence Meiosis occur