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Chapter 1

KIN 1Y03- chapter 1- terminology and the body plan.docx

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Krista Howarth

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KIN 1Y03- Terminology and the Body Plan- Chapter 1 Anatomy and Physiology - Anatomy is the scientific discipline that investigates the body’ structure. - Can be considered at different levels. - Developmental anatomy is the study of structural changes that occur between conception and adulthood. - Embryology considers changes from conception to the end of the eighth week if development. - Cytology examines the structural features of cells. - Histology examines tissues. - Systemic anatomy studies the body system by system. - Regional anatomy the body is studied area by area. - Surface anatomy is the study of the external form of the body. - Physiology is the scientific investigation of the processes or functions of living things. - Pathology is the medical science dealing with aspects of disease. - Exercise physiology focuses on changes in function, caused by exercise. Structural and Functional Organization - Six levels of organization. - Chemical level : involves interactions between atoms. - Cell level : cells are the basic structural and functional units of organisms such as plants and animals. Molecules can combine to form organelles. - Tissue level: a tissue is a group of similar cells and the materials surrounding them. The characteristics of the cells and surrounding materials determine the functions of the tissue. Four basic types of tissue in the body: epithelial, connective, muscle and nervous. - Organ level: an organ is composed of two or more tissue types that perform one or more common functions. - Organ system level: an organ system is a group of organs that have a common function or set of functions and are viewed as a unit. - Organism level: an organism is any living thing considered as a whole. Characteristics of Life - Living things are highly organized. - Disruption of this organized state can result in loss of functions, even death. - Metabolism is all of the chemical reactions taking place in an organism. - Responsiveness is an organism’s ability to sense changes in its external or internal environment and adjust to those changes. - Growth happens when a cells increase in size and number. - Development includes the changes an organism undergoes through time. - Differentiation is change in cell structure and function from generalized to specialized and morphogenesis is change in the shape of tissues, organs, and the entire organism. Homeostasis - Homeostasis is the existence and maintenance of a relatively constant environment within the body. - For cells to function properly the volume, temperature and chemical content , variables, must remain within a constant range in the fluids that surround each cell. - Negative feedback is when any deviation from the set point is made smaller or is resisted. - Many negative feedback system have three components ; a receptor, a control center and an effector. - Positive feedback is when a deviation from a normal value occurs, the system’s response is to make the deviation even greater; Terminology and the Body Plan - Anatomical position refers to a person standing erect with the face directed forward, the upper limbs hanging to the sides, and the palms of the hands facing forward. - Supine is lying face upward. - Prone is lying face downward. - Up is replaced by superior. - Down is replaced by inferior. - Front is anterior. - Back is posterior. - Superior is synonomous with cephalic, meaning toward the head, - Inferior in synonymous with caudal, meaning toward the tail. - Ventral means belly. - Dorsal means back. - Proximal means nearest. - Distal means distant. - Proximal and distal are used to describe linear structures, such as the limbs. - Medial means toward the midline, lateral means away from the midline. - Superficial refers to a structure close to the surface of the body, deep is toward the interior of the body. Body Parts and Regions - The upper limb is divided into the arm. Forearm, wrist and hand. - The arm extends from the shoulder to the elbow, and the forearm extends from the elbow to the wrist. - The lower limb is divided into the thigh, leg, ankle and foot. - The thigh extends from the hip to the knee, leg from the knee to the ankle. - The central region of the body consists of the head, neck and trunk. - The trunk can be divided into the thorax, abdomen and pelvis. Planes - A plane divides or sections, the body making it possible to look inside and observe the body’s structures. - A sagittal plane runs vertically through the body. - A median plane is a sagittal plane dividing the body into equal right and left planes. - A transverse, or horizontal plane runs parallel to the ground, dividing the body into superior and inferior positions. - A frontal or coronal plane runs vertically from right to left and divides the body into anterior and posterior parts. - Organs are often sectioned to reveal their internal structure. - A cut through the long axis of the organ is a longitudinal section. - A cut at right angles to the long axis is a cross or transverse section. - If a cut is made across the long axis other than at a right angle it is called an oblique section. Body Cavities - The trunk contains three cavities that do not open to the outside of the body. - The thoracic, abdominal and the pelvic. - The rib cage surrounds the thoracic cavity, and the diaphragm separates it from the abdominal cavity. - The thoracic cavity is divided into right and left by a median partition called the mediastinum. - The mediastinum contains the heart, trachea, esophagus, thymus, and other structures such as blood vessels and nerves. - Abdominal muscles enclose the abdominal cavity which contains the stomach, intestines, liver, spleen, pancreas and kidneys. - Pelvic bones encase the pelvic cavity where the urinary bladder, part of the large intestine and internal reproductive organs are housed. - The abdominal and pelvic cavities are not physically separated and are sometimes called the abdominopelvic cavity. Serous Membranes - Serous membranes cover the organs of the trunk cavities and line the trunk cavities. - Inflated balloon into which a fist has been pushed. - Fist represents an organ, the inner balloon wall represents the visceral serous membrane and the outer balloon wall represents the parietal serous membrane. - The cavity between the membranes is filled with a thin, lubricating film of serous fluid produced by the membranes. - The thoracic cavity contains three serous membrane lined cavities: a pericardial cavity and two pleural cavities. - The pericardial cavity surrounds the heart. - The visceral pericardium covers the heart, which is contained within a connective tissue sac lined with parietal pericardium. - Pericardial cavity is located between the visceral and parietal pericardium - A pleural cavity surrounds each lung, which is covered by visceral pleura. - Parietal pleura line the inner surface of the thoracic wall, the lateral surfaces of the mediastinum and the superior surface of the diaphragm. - The abdominopelvic cavity contains a serous membrane lined cavity called the peritoneal. - Visceral peritoneum covers many of the organs, and parietal peritoneum lines the wall of the abdominopelvic cavity and the inferior surface of the diaphragm. - Mesenteries which consist of two layers of peritoneum fused together, connect the visceral peritoneum of some abdominopelvic organs to the parietal peritoneum on the body wall or to the visceral peritoneum on other orgnas. - The mesenteries anchor the organs to the body wall, and provide a pathwanchor the organs to the body wall, and provide a pathway for nerves and blood vessels to enter organs. - Other abdominopelvic organs are more closely attached to the body wall, and do not have mesenteries. - Parietal peritoneum covers these organs which are said to be retroperitoneal. - Includes the kidneys, adrenal glands, pancreas, parts of the intestines and the urinary bladder. Chapter 29 – growth development and aging - The prenatal period is the period from conception until birth. - It is divided into three parts : - Germinal- the first two weeks of development, during which the primitive germ layers are formed. - Embryotic – from about the second to the end of the eighth week, during which the major organ systems come into existence. - Fetal – last 30 weeks of the prenatal period, during which the organ systems grow and become more mature. - The medical community uses the mother’s last menstrual period (LMP) to calculate the clinical age of the unborn child. - Most embryologists use post-ovulatory age, which is 14 days less and clinical. Fertilization - The process by which a sperm cell attaches to a secondary oocyte, the contents of the sperm head enter the oocyte cytoplasm and join the oocyte pronucleus to form a new nucleus. - The vicinity of the secondary oocyte is the ampulla of the uterine tube. - The corona radiate, are cells of cumulus mass expelled from the follicle with the oocyte, is a barrier to the sperm cells reaching the oocyte. - Sperm cells are propelled through the loose matrix between the follicular cells of the corona radiate using their flagella. - The zona pellucida is an extracellular membrane comprised mostly of glycoproteins , between the corona radiate and the oocyte. - One specific glycoprotein is called ZP3, a species-specific sperm cell receptor to which molecules on the acrosomal cap of the sperm cell bind. - This initiates the acrosomal reaction, which results in the activation of digestive enzymes, primarily hyaluronidase, in the acrosome. - The first sperm cell through the zona pellucida attaches to the integrin a6B1, on the surface of the oocyte plasma membrane. - This causes the depolarization within 2-3 seconds of sperm cell attachment. - This depolarization is called the fast block to polyspermy. - Depolarization also causes the intracellular release of Ca 2+, which causes the exocytosis of water and other molecules from secretory vesicles, referred to as cortical granules. - The released fluid causes the oocyte to shrink and the zona pellucida to denature and expand away from the oocyte. - ZP3 is inactivated and no additional sperm cells can attach. - This is called the slow block to polyspermy. - The fast and slow block ensure that the oocyte is fertilized by only one sperm cell. - The fluid filled space between the oocyte plasma membrane and the zona pellucida is called the perivitteline space. - The entrance of a sperm cell into the oocyte stimulates the female nucleus to undergo the second meiotic division and the second polar body is formed. - The nucleus that remains after the second meiotic division is called the female pronucleus, moves the the center of the oocyte where it meets the male pronucleus of the sperm cell. - Both pronucleuses are haploid, they fuse which completes the process of fertilization and restores the diploid number of chromosomes. - The product of fertilization is a single cell, the zygote. Early Cell Division - About 18-36 hours after fertilization, the zygote divides to form two cells. - Divides into four cells etc. - In the very early stages of development (days 1-4) the cells are said to be totipotent, meaning each cell has the potential to give rise to any tissue type necessary for development. - At this point if the totipotent cell separate from the embryo it could give rise to another individual, identical twins. - The cells soon undergo differentiation, or specialization. - Once differentiation occurs the dividing cels of the embryo are referred to as pluripotent, which means that any cell has the ability to develop into a wide range of tissues but not all tissues necessary for development. - As a result the total number of embryonic cells can decrease, increase or reorganize without affecting the normal development of the embryo. - In rare cases, following early cell divisions, the cells separate and develop to form two individuals, called identical or monozygotic twins. - They have identical genetic info. - Fraternal or dyzigotic twins form when a woman ovulates two or more oocytes and they are fertilized by different sperm cells. Morula and Blastocyst - Once the cell is a solid ball of 12 or more cells, it is called a morula. - 4 or 5 days after ovulation the morula consists of about 32 cells. - Near this time, a fluid filled cavity called the blastocele begins to appear around the center of the cellular mass. - The hollow sphere that results in the blastocyst. - A single layer of cells, the trophoblast, surrounds most of the blastocele, but at one end of the blastocyst the cells are several layers thick. - This is called the inner cell mass, and is the tissue from which the tissue from which the embryo proper develops. - The pluripotent cells of the inner cell mass do not form all the tissues necessary for normal development. - The trophoblast forms the placenta and the membranes (chorion and amnion) surrounding the embryo. Implantation of the Blastocyst and Development of the Placenta - All of the events of the early germinal phase occur as the embryo moves from the site of fertilization in the ampulla of the uterine tube to the site of implantation in the uterus. - About 7 days after fertilization the blastocyst attaches itself to the uterine wall and begins the process of implantation, burrowing of the blastocyst into the uterine wall. - As the blastocyst invades the uterine wall, two populations of trophoblast cells develop and form the embryonic portion of the placenta. - The first is a proliferating population of individual trophoblast cells called the cytotrophoblast. - The other is a nondividing syncytium or multinucleated cell, called the syncytiotrophoblast. - The cytotrophoblast remains nearer the other embryonic tissues and the syncytiotrophoblast invades the endometrium of the uterus. - As the syncytiotrophoblast encounters maternal blood vessels, it surround them and digests the vessel wall, forming pools of maternal blood within cavities called lacunae. - The lacunae are still connected to intact maternal vessels so that blood circulates from the maternal vessels through the lacunae. - Cords of cytotrophoblast surround the syncytiotrophoblast and lacunae. - Branches called chorionic villi, sprout from these chords and protrude into the lacunae. - The entire embryonic structure facing the maternal tissues is called the chorion. - Embryonic mesoderm and blood vessels grow into the cords and villi as they protrude into the lacunae. - In the mature placenta, the cytotrophoblast disappears so that the embryonic blood supply is separated from the maternal blood supply by only the embryonic capillary wall, a basement membrane and a thin layer of syncytiotrophoblast. Formation of the Germ Layers - After implantation, a new cavity called the amniotic cavity forms inside the inner cell mass and is surrounded by a layer of cells called the amnion or amniotic sac. - Formation of the amniotic cavity causes part of the inner cell mass nearest the blastocele to separate as a flat disk of tissue called the embryonic disk. - This embryonic disk is composed of two layers of cells : an ectoderm, adjacent to the amniotic cavity and an endoderm, on the side of the disk opposite the amnion. - A third cavity, the yolk sac, forms inside the blastocele from the endoderm. - Amniotic sac and yolk sac are like two balloons pushed together, and the embryonic disk is the double layer of balloon in the middle. - The amniotic sac eventually enlarges to surround the developing embryo, providing it with a protective fluid environment. - About 13 or 14 days after fertilization, the embryonic disk becomes a slightly elongated oval structure. - This phase of development, known as gastrulation involves the movement of cells, resulting in the formation of three distinct germ layers. - Proliferating cells of the ectoderm migrate toward the center and the caudal end of the disk forming a thickened line called the primitive streak. - Some ectoderm cels leave the ectoderm, migrate through the primitive streak and emerfe between the ectoderm and endoderm as a new germ layer, the mesoderm. - These three germ layers, ectoderm, mesoderm and endoderm, are the beginning of the embryo proper. - A cordlike structure called the notochord extends from the cephalic end if the primitive streak. - Some of the cell communication depends on cell-cell contact, whereas other communication depends on diffusible molecules, such a growth factors. Two important families of growth factors are epidermal growth factors and fibroblast growth factors. Neural tube and neural crest formation - The ectoderm near the cephalic end of the pri
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