Lecture Notes week one
Lecture Notes week one Biol 221
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This 12 page Class Notes was uploaded by Katlyn Burkitt on Thursday September 8, 2016. The Class Notes belongs to Biol 221 at Towson University taught by Williams-Hogarth in Fall 2016. Since its upload, it has received 93 views. For similar materials see Human Anatomy and Physiology 1 in Biology at Towson University.
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Date Created: 09/08/16
Anatomy and Physiology Day One 29.1 Development, marked by various stages, is a continuous process that occurs from fertilization to maturity (Pg. 1096) Development: The gradual modification of anatomical structures and physiological characteristics during the period from fertilization to maturity Differentiation: The process through which different types of cells required for specialized functions. This occurs through selective pressures that call for some genes to be turned off and some to be turned on Fertilization/Conception: Where the male and female gametes fuse and development begins Embryonic development: Includes events during the first two months after fertilization o The study is called embryology Fetal development: The events beginning in the ninth week and continuing until birth Prenatal development: An umbrella term for embryonic and fetal development Postnatal development: Begins at birth and continues until maturity Maturity: The state of full development or completed growth Inheritance/ Heredity: The transfer of genetically determined characteristics from generation to generation Genetics: The study of the mechanisms responsible for inheritance 29.2 Fertilization-The fusion of a secondary oocyte and a spermatozoon forms a zygote. (pg. 1097) Zygote: The fusion of the two haploid cells (fertilization) Capacitation: The physical changes in the spermatozoa (Plural of Spermatozoon) coating and uncovering of receptors that allow it to penetrate and fertilize an oocyte *occurs due to secretions from the seminal glands* st o 1ndtep in male reproductive tract o 2 in female They cannot accomplish fertilization until they are exposed to conditions in the female reproductive tract Uterine tube peg cell secretions assist with capacitation but the exact mechanism responsible for capacitation remains unknown Fertilization takes place near the junction of between the ampulla and isthmus of the uterine tube, generally within 1 day of ovulation By the end of day 1 of ovulation the secondary oocyte has traveled a few centimeters but the spermatozoa must cover the distance between the vagina and the ampulla of the uterine tube A spermatozoon can travel at a distance of 12.5 cm per hour (5in), typically takes between 2hours and 30mins for it to travel due to contractions of the uterine muscles and ciliary currents in the uterine tube assisting in the movement from the vagina to the site of fertilization 200million spermatozoa are introduced into the vagina by a typical ejaculation, 10,000 enter the uterine tube, >100 make it to the isthmus Despite only one Spermatozoon fertilizing the oocyte (Egg cell), multiple are required because one does not have enough acrosomal enzymes to disrupt that corona radiata Corona radiata: The layer of follicle cells that surround the oocyte Subsection: The Oocyte at Ovulation Ovulation takes place before the oocyte is fully mature The secondary oocyte is in metaphase of meiosis II and its metabolic operations are suspended until stimulus in the form of fertilization is introduced. If it is not introduced, then the oocyte disintegrates without completing meiosis. Fertilization is complicated by the Corona radiata that coats the secondary oocyte when it leaves the ovary Fertilization only requires one spermatozoon to contact the oocyte embrace, but that spermatozoon must first penetrate the corona radiata. The acrosome of each sperm contains several enzymes o Hyaluronidase: The enzyme that breaks down the bonds between adjacent follicle cells Dozens of spermatozoa must release hyaluronidase before the connections between the follicle cells break down enough to allow an intact spermatozoon to reach the oocyte Only one spermatozoon fertilizes and activates the oocyte even if multiple enter the gap in the corona radiata and must have an intact acrosome o Step 1: The binding of the spermatozoon to sperm receptors in the Zona Pellucida Zona Pellucida: A thick envelope surrounding the oocyte o Step 2: The binding triggers the rupture of the acrosome o Step 3: The rupture of the acrosome releases hyaluronidase and acrosin (another protein digesting enzyme) o Step 4: The two proteins digest a path through the Zona Pellucida toward the surface of the oocyte o Step 5: The spermatozoon then reaches the surface of the oocyte and the membranes of each begin to fuse. Trigger oocyte activation Oocyte Activation o A series of changes in the metabolic activity of the oocyte. o This is triggered by contact and fusion of the membranes of the sperm and oocyte o It is accompanied by the depolarization of the oocyte membrane due to increased permeability to sodium ions o The entry of sodium ions causes a release of calcium ions from the smooth ER and the sudden rise in Calcium causes Exocytosis of Vesicles adjacent to the Oocyte Membrane Called Cortical reaction Releases enzymes called zonal inhibiting proteins (ZIPS) These enzymes inactivate the sperm receptors and harden the Zona Pellucida This prevents polyspermy (The fertilization by more than one sperm which would create a zygote incapable of normal development) It is likely that the depolarization of the oocyte membrane prevents fertilization by any other sperm that penetrates the Zona Pellucida before the completion of the Cortical reaction Completion of meiosis II and the formation of the second polar body The sperm enters the oocyte and loses its plasma membrane Meiosis 2 which began in the tertiary follicle can now be completed Oocyte is now called an Ovum Activation of enzymes that cause a rapid increase in the cells metabolic rate The mRNA contained in the cytoplasm is now activated and rapidly completes protein synthesis After the completion of meiosis, the nuclear material remaining within the ovum reorganizes as the female pronucleus While the female pronucleus is forming the nucleus of the spermatozoon swells and forms the male pronucleus and the rest of the sperm cell breaks down Then the male pronucleus moves to the center of the cell and spindle fibers form The male and female pronuclei fuse through a process called amphimixis (Metaphase of meiosis 2) The cell is now a zygote with 46 chromosomes and fertilization is complete *The moment of conception* Then the chromosomes line up along the metaphase plate and the cell prepares to divide This is the start of cleavage: A series of cell divisions that produce an increasing number of ever shrinking daughter cells. The zygote becomes a pre-embryo The first cleavage is complete approx. 30hours after conception Blastometers: The smaller daughter cells produced during cleavage they are approx. ½ the size of the original 29.3 Gestation consists of three stages of prenatal development: The first, second, and third trimesters Prior to ovulation the oocyte accepts amino acids, nucleotides, glucose, phospholipids, mRNA, and proteins from the surrounding granulosa cells The cytoplasmic composition is not evenly distributed because not all follicle cells manufacture and deliver the same nutrients and instructions Because it divides into even smaller daughter cells their cytoplasmic composition differs from one another creating increasingly diverse fates. As it continues some cells release RNA molecules, polypetides, and small proteings that affect the differentiation of other embryonic cells o This is called induction and only works when cells are in directing contact Gestation: The time spent in prenatal development Trimesters: Three month intervals of gestation, a total of 3. o 1 Trimester: Embryonic and early fetal development o 2 ndTrimester: The period dominated by the development of organs and organ systems rd o 3 Trimester: Characterized by rapid fetal growth and deposition of adipose tissue, most major organ systems are fully functional, fetus is viable 29.4 Cleavage, implantation, placentation, and embryogenesis are critical events in the first trimester Implantation: When the blastocyst attaches to the endometrium of the uterus. It continues as the blastocyst invades maternal tissues Placentation: Blood vessels form around the periphery of the blastocyst and the placenta (a complex organ that permits exchange between maternal and embryonic blood that supports the fetus from formation to birth) Embryogenesis: The formation of a viable embryo Only 40% of conceptions produce embryos that survive the first trimester Cleavage and Blastocyst formation o After the first division divisions take place at intervals of 10-12 hours and divide simultaneously o Morula: The pre-embryo at 3 days of cleavage and reaches the uterus around day 4 o Blastocyst: A hollow ball with an inner cavity called a blastocoele o Trophoblast: The outer layer of cells of the blastocyst that provide nutrients to the developing embryo o Inner cell mass: A group of cells clustered at one end of the blastocyst and exposed only to the blastocoele insulated from outside uterine environment and will form the embryo Implantation o Enzymes released by the trophoblast erode an opening in the zona pellucida which will be shed in a process known as hatching o The blastocyst is now exposed to the fluid contents of the uterine cavity o It now absorbs the glycogen-rich fluid secreted by the uterine glands and enlarges o When fully formed it contacts the endometrium and implantation takes place o Begins when the surface of the blastocyst closest to the inner cell mass adheres to the uterine lining o At the point of contact the trophoblast cells divide rapidly making several layers o The cells closest to the interior of the blastocyst remain intact forming the cellular trophoblast or cytotrophoblast o Near the endometrial wall the plasma membranes separating the trophoblast cells disappear creating a cytoplasm with multiple nuclei. This outer layer is called a syncytiotrophoblast o The cells dissolve the uterine epithelium using hyaluronidase (same enzyme that broke down the corona radiata) o The erosion causes a gap in the uterine lining that is then repaired by maternal epithelial cells and by 10 the repairs are complete and the blastocyst does not have contact with the uterine cavity o Development now occurs in the functional zone of the endometrium o Fundus: The body of the uterus where implantation typically occurs o Ectopic pregnancy: Implantation occurring in a location other than the fundus o The syncytial trophoblast continues to enlarge and spread through the endometrium and absorb nutrients into the inner cell mass o These provide energy for early embryo formation o Trophoblastic extensions grow around the endometrial capillaries and as the capillary walls are destroyed releasing maternal blood into lacunae (Trophoblastic channels) o Spreading until day 21 o Formation of Amniotic Cavity (fluid filled chamber) The Inter cell mass separates Superficial layer (Epiblast): Exposed to the amniotic cavity Deeper layer (Hypoblast): Exposed to the blastocoele Cells from the Epiblast differentiate and line the amniotic cavity Cells from the Hypoblast differentiate and form the membrane for the yolk sac (absorbs and distributes nutrients absorbed through the trophoblast) o Gastrulation and Germ layer formation Formation of 3 layer of cells Superficial cells of the blastodisc migrate toward the central line known as the primitive streak o Germ layers Migrating cells leave the surface and move between 2 existing layers (Epiblast + Hypoblast) which forms 3 layers called germ layers The Ectoderm: Consisting of superficial cells that did not migrate into the interior of the blastodisc Endoderm: Consisting of cells that face the yolk sac Mesoderm: Consisting of the poorly organized layer of migrating cells between the ectoderm and the endoderm This formation of the germ layers produces the embryonic disc that will later form the body of the embryo Formation of Germ layers forms four extraembryonic membranes o Yolk sac A pouch of cells that serve as the primary source for early embryonic development o Amnion Ectodermal cells that spread over the inner surface of the amniotic cavity; amniotic fluid is produced and cushions the developing embryo o Allantois An out pocket of the endoderm near the base of the yolk sac that grows toward the wall of the blastocyst surrounded by mesodermal cells, eventually gives rise to the urinary bladder. o Chorion Blood vessels develop to create a rapid- Transit system for nutrients that link the embryo with the trophoblast Chorionic villi continue to enlarge the branch creating a network in the endometrium where embryonic blood vessels Step one of forming the placenta Placentation o Entire blastocyst is surrounded by chorionic villi o It enlarges like a balloon o By week 4 the embryo, amnion, and yolk sac are suspended within a fluid filled chamber o Body stalk: The connection between the embryo and chorion contains the distal allantois and blood vessels o Yolk Stalk: The connection between the endoderm of the embryo and yolk sac o Decidua Capsularis???? o Decidua basalis???? o Decidua parietals???? o Umbilical cord: The connection between the fetus and placenta Placental Circulation o Umbilical arteries: Paired arteries that take blood from the fetus to the placenta o Umbilical vein: Returns blood from the placenta to the fetus Endocrine Placenta o Human Chorionic Gonadotropin A hormone that indicates pregnancy Maintains the integrity of the corpus luteum Promotes the continued secretion of progesterone Without this pregnancy ends because another uterine cycle begins o Human placental lactogen and placental prolactin Helps to prepare the mammary glands for milk production Ensures that glucose and protein are available for the fetus o Relaxin A peptide horone secreted fby the placenta and the corpus luteum during pregnancy Increased the flexibility of the pubic symphysis allowing the pelvis to expand for delivery Causes the cervix to dilate allowing the fetus to enter the vaginal canal Suppresses the realease of oxytocin by the hypothalamus which delays the onset of labor contractions o Progesterone/ Estrogens Maintains the endometrial lining Continues pregnancy Embryogenesis : The body of the embryo and the internal organs begin to form Head fold : The fold that will later become the head of the developing fetus Tail fold: The fold that will later begin the lower body of the fetus Organogenesis: The process of organ formation 4.1 The four tissue types Tissues o Collections of specialized cells and cell products that carry out limited functions Histology o The study of tissues Epithelia tissues o Tissues that cover exposed surfaces, lines internal passageways and champers, and forms glands Connective tissues o Fills internal spaces, provides structural support, transports materials within the body, and store energy Muscle tissue o Specialized tissue for contraction Neural tissue o Carries information in the form of electrical impulses 4.2 Epithelia tissue Cellularity o High density of cells in small areas Polarity o Is polar Apical surface o The part of the cell that faces the external environment Basal surface/ Basolateral surfaces o The part attached to the basement membrane/basal lamina Avascularity o They do not have blood vessels Regeneration o Functions of Epithelial Tissue Provide physical protection Control permeability Provide sensation Produce specialized secretions Glandular epithelium Specialization of Epithelial Cells Cilia Ciliated epithelium Intercellular connections Maintaining the integrity of the Epithelia Cell adhesion molecules (CAMs) o Adhesion molecules that are transmembrane and exist inside the membrane to prevent entry into tissue Intrercellular cement o Proteoglycans (High in sugar) Hyaluronan (Includes hyaluronic acid) o Glycosaminoglycans (GAGS) o Can be broken down by hyrulodase (found in the head of sperm and the blastocyte) Cell junctions Gap junctions o Lateral portion of the cells o Allow rapid communication and the diffusion of ions o Held together by channel proteins (Connexons) Tight junctions o Present at apical ends of tissue o Between two plasma membranes o Prevents passage of fluids between cells and from the external to internal environment o Connected through interlocking junctional proteins Adhesion belt o Underlying structure in a tight junction o Attaches to the terminal web (Micro filaments inside cells) o Uses cellular adhesion molecules Lumen o Lining of a hollow organ Desmosome o Like a ligament to a cell, allows cells to bind to each other o Have CAMs, dense areas, and intercellular cement o Dense areas: Allows cellular adhesion molecules to be imbedded o Spot desmosomes Tie cells together Allow bending and twisting Lateral side o Hemidesmosomes Attach cells to the basement membrane Basal surface Clear layer Produce by the epithelia cells Serves as a barrier Dense Layer Produced by underlying connective tissue Thick fibers Strength Epithelial maintenance and repair Stem cells/Germinative cells o Exist to repair the epithelia o Near basement membrane 4.3 Cell shape and number of layers Simple Epithelium o Single layer of cells Stratified Epithelium o Several layers of cells Pseudostratified o Appears stratified but is not Squamous epithelium o Thin and flat Simple Squamous epithelium o Single layer of thin and flat cells o Is useful for absorption and diffusion o Allows for rapid diffusion and secretion o Reduces friction o Controls permeability o Mesothelium Lines the bodies cavities o Endothelium Lines heart and blood vessles Stratified squamous epithelium o Multiple layers of thin and flat cells o Protects against attacks o Keratin Binding protein that adds strength and water resistance o Keratinized Has Keratin in it o Nonkeratinized Does not have Keratin in it Cuboidal Epithelium o Square shaped Simple cuboidal epithelium o Secretion absorption Stratified cuboidal epithelia o Multiple layers of square shaped o Create a lot of secretions, sweat ducts and mammary ducts Transitional Epithelium o Tolerates cycles of stretching and recoiling and returns to its previous shape without damage o Appearance changes as stretching occurs Columnar epithelial cells o Tall, slender rectangles o Simple Columnar epithelium Single layer Absorption and secretion o Pseudostratified columnar epithelium Single layer of tall slender cells that looks like more than one layer Cilla movement Typically, in the respiratory tract o Stratified Columnar epithelia Multiple layers of tall slender cells Protection Gladular epithelia o Endocrine glands (ductless glands) Release hormones Into interstitial fluid No ducts o Exocrine glands Produce secretions Onto epithelial surfaces Done through ducts Secretions Merocrine secretion Produced in the Golgi apparatus Released by vesicles through exocytosis Ex. Sweat glands Apocrine secretion Produced in the Golgi apparatus Released by vesicles by shedding cytoplasm Ex. Mammary glands Holocrine secretion Released by cell bursting, killing gland cells Gland cells replaced by stem cells Ex. Sebaceous glands o Oil producing glands on skin and hair Types of secretion o Serous glands Watery o Mucous glands Secrete mucins o Mixed exocrine glands Both serous and mucous Unicellular glands o Mucous (goblet) cells (only type) Scattered along epithelia Ex. Intestinal lining Multicellular glands o Structure of the duct Simple (Undivided) Compound (divided) o Shape of secretory portion of the gland Tubular (tube shaped) Alveolar/ Acinar (blind pockets) Duct cells cannot secrete o Relationship between ducts and glandular areas Branched More than one secretory portion More than one duct Unbranched More than one secretory portion Only one duct
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