MCB 135 E Exam I Review Jason Lowry

MCB 135 E Exam I Review Jason Lowry Fall 2005

General Information • Exam I – Wednesday 10/5/04 – In-class exam (50 minutes, 100 points) – You will need a pencil and a pen – If you write short answers in pencil, they are not eligible for regrade – We will provide a scantron – You will need to place everything except pen/pencil at the front of room or in the aisle (NOT UNDER THE CHAIR) – The exam will not begin until everyone has complied

General Information • Exam I – Material for exam will cover everything through the lecture on Monday (10/3/05) – Exam breakdown – Exam questions are based on lecture material (not website nor discussion)

Review Material • • Reproductive Systems Fertilization and Implantation Embryonic Development The placenta and hormones of pregnancy Nervous System Development Sexual Differentiation Metabolism and Growth

Gametogenesis • Spermatogenesis – What is it – Where does it occur – What are the hormones involved – What is the progression of sperm maturation – What are the major characteristics of sperm

Spermatogenesis • Formation of Spermatozoa (Sperm) • Occurs in seminiferous tubules • Involves two distinct maturational processes – Spermatocytogenesis • 1 st Stage of sperm formation • Spermatogonium Spermatids • Involves mitosis(46 Chromosomes) initially and then meiosis (23 Chromosomes) – Spermiogenesis • Spermatids Spermatozoa

Male Reproductive Endocrinology

Gametogenesis • Oogenesis – What is the function of the ovaries – What is the process of oogenesis – What are the hormones involved – How are these hormones regulated

The Ovaries • Gamete producers • 3 cm long solid mass of cells • Suspended in the abdomen by ligaments and mesenteries • Oocytes found on outside surface of ovaries

Oogenesis • • Primary Oocytes form at 3 months during fetal development 2 million primary oocytes by birth in prophase of first meiotic division Maturation – Increased size and Meiosis First meiotic division resumes a few hrs before ovulation due to LH Surge • Second meiosis after fertilization • • • Division produces unequal mass of cells most food goes to ovum and none to polar body. All polar bodies die eventually. Oocyte+specialized cells=follicle: Nourish ovum and secrete estrogens Mature follicle bursts releasing ovum. Many follicles enlarge but only one bursts.

Gamete Comparison • Male – – – Sperm Small Size Elongated Shape Millions in # Vigorous Motility No protecting envelope Minimal Cytoplasm Lacks yolk Centrosome Retained Mitochondria in body Golgi Apparatus in acrosome – Nucleus condensed in head – XY • Female – – – – Ovum Large size Spheroidal shape Few in # Lack motility Egg envelopes for protection Bulky Cytoplasm Little Yolk Centrosome Disappears Diffuse mitochondria Diffuse golgi apparatus Open structured nucleus XX

Fertilization and Implantation – Fertilization • • • Sperm Morphology Organization of ovum after ovulation Role of ovum in fertilization Role of sperm in fertilization Stages of fertilization What is capacitation, acrosomal reaction, zona pelucida – Implantation • Pre-implantation events • Act of implantation

Morphology

Fertilization • Role of Ovum – Contribute the maternal complement of genes – Reject all sperms but one – Provide food reserve until the embryo begins to feed upon exogenous material • Role of Sperm – Reach and penetrate the egg – Activate the egg to nuclear and cytoplasmic division necessary to embryonic development – Contribute the paternal complement of genes

Stages of Fertilization • Penetration – Random contact between sperm and egg – Sperm propel past corona cells and attach to zona pelucida – One sperm-One Egg • Activation – Completion of Meiosis of ovum – forms female pronucleus – Sperm Changes – Sperm travels toward center of egg, head swells, becomes male pronucleus – Rearrangement in egg – biochemical changes necessary prior to nuclear fusion • Nuclear Fusion – Union of two pronuclei – Loss of nuclear envelope, contribution of chromosomes to first mitotic cleavage

Uterine Preparation • Estrogen – Involved in proliferation of uterus (hypertrophy) – 3 -5 Days post-ovulation E dominates and is thought to play a role in transport of ovum • Progesterone – Increased Vascularization (hypervascularization) – 5 -7 days post-ovulation, P increases and counters the effect of E thus relaxing uterine contractions

Implantation • Days 1 -8 – Fertilized egg begins to divide by cleavage into smaller blastomeres – Blastomere increase follows a double synchronous sequence initially, but later becomes asynchronous – Later stage cleavage forms a ball of cells or morula – Fluid begins accumulating in morula and a conversion occurs to the blastula (blastocyst) – Blastocyst attaches to uterine stroma – Outer layer of cells begin to proliferate and invade stroma of uterus

Implantation • Days 8 -16 – Blastocyst lodged in uterine stroma – Trophoblast (outer cells) invades uterine stroma and begins to form placenta – Blastocele becomes chorionic cavity – Inner cell mass begins to proliferate and form germ disc and primitive entoderm – Complex sequence of chemical and physical interactions occur between ovum and mother • Only about 50% of fertilized eggs successfully implant

Embryonal Development • Germ Layer Theory • Gastrulation • Tissues generated

Germ Layer Theory • Embryo’s Method of sorting out its parts – Ectoderm – Outer covering of embryo – Entoderm (Endoderm) – Lies under the ectoderm and forms lining of the primitive gut cavity – Mesoderm – Develops between ectoderm and entoderm • Gastrulation – The process by which germ layers come to occupy their characteristic positions

Germ Layers and Their Systems • Ectoderm – – – – Epidermis and lining cells of glands Appendages of skin Nervous system Posterior Pituitary Chromafin organs - adrenal medulla Anterior Pituitary Some Epithelium • Entoderm – – Epithelial lining of alimentary canal Lining cells of glands that open to alimentary canal Epithelium of most of the urinary bladder and urethra Epithelium of prostate • Mesoderm – – – Remaining organs and tissues not made by Ectoderm or Entoderm Connective tissue Teeth Musculature Blood Adrenal Cortex

Placenta and Hormones of Pregnancy • Structure of placenta – Include • Fetal membranes • Maternal membranes • Functions of placenta – Hormones • Role of hormones • Hormone Biosynthesis – Respiration – Protection – Excretion • Fetal circulation – Trace blood flow – Know obstacles – Know modifications

Placenta • Fetal 1. 2. 3. Yolk Sac – Center of blood formation in early embryonal life – Facilitates transfer of nutrients from developing trophoblast to embryo Allantois – Blood vessels develop around allantoic tube – Tube eventually fuses with chorion – By 6 th week – 1 umbilical vein and 2 umbilical arteries Amnion – Membranous sac that surrounds embryo – Fluid fills amnion that has protective role throughout pregnancy • Maternal Deciduas – Highly modified uterine endometrium a) Basalis • Portion between ovum and uterine wall b) Capsularis • Region of decidua where ovum is embedded c) Parietalis • Lines remainder of uterus

Placenta Functions • • • Gas Exchange Nutrient Delivery Antibody Delivery Removal of Waste Secretion of hormones Protection

Hormones of Pregnancy • • • Estrogen Progesterone h. CG Placental Lactogen (h. CS) Placental Growth Hormone

Steroid Hormone Synthesis

Challenges and Adaptations • Challenge – Oxygen and Nutrients are less in umbilical vein than in adult arteries • Adaptations – Establish priorities – Establish specific structures to supply priorities – Embryonal Hemoglobin

Specific Structures 1. Ductus Venosus • Shunts Umbilical Vein to Inferior Vena Cava 2. Foramen Ovale • Shunts between atria 3. Ductus Arteriosus • Shunts pulmonary artery to aorta

Nervous System • Major Functions – Communication with external/internal environment – Regulation of… • Major Components – – – Neurons Neuroglia Mylenated nerve fibers Microglia Ground Substance Blood Vessels and CSF

Development of the Nervous System • • Morphological Development Biochemical Development Functional Development Sexual Differentiation

Neurulation • N. S. – Arises from ectoderm on dorsal portion of embryo • 3 -4 Weeks – Cells proliferate along middle plate • 5 -6 Weeks – Plate folds to form neural groove • 6 -7 Weeks – Groove closes into neural tube – Brain develops from anterior portion – Spinal cord develops from the posterior portion

Neural Epithelium • Neuroblast – Neuron • Spongioblast – Migratory Spongioblast • Oligodendria • Astrocytes – Ependyma

Energy Sources • Carbohydrates – Primarily maternal glucose – Stored as glycogen • Under influence of glucocorticoids • In fetus – Insulin levels high – Insulin sensitivity high – Hypoglycemic • Anaerobic Glycolysis – Glyceraldehyde-PDehydrogenase • Glycolitic enzyme • High in postnatal brain • During same period the oxidative enzyme – Succinic Dehydrogenase – Much lower

Thyroid Hormone • Functions – Promotion of body growth – Development of CNS through: • Promotion of neorogenesis • Promotion of myelination • Promotion of brain metabolism – Stimulates oxygen consumption in all cells • Abnormalities – Hypothyroidism • Cretinism • Short stature, low metabolic rate, skin changes • Treatable if given Thyroxine at an early age

Functional Development • Differential Development of N. S. – Neurotransmitter activity in different brain regions • Perinatal Behavior – Reflexes – Refer to table in reader • Motor • Respiratory (17 -24 weeks) • Gastrointestinal (24 th week) – Suckling • Startle (Presence of excessive activity after birth is an indicator of delayed development of certain brain centers) • Education – Better educated appear to live longer with less disability – Several pieces of evidence discussed for this in class

Sexual Differentiation

Sexual Differentiation • Steroid hormone action on brain development – Androgen action on sexually dimorphic nucleus of the preoptic area (SDN-POA) • Male Rats – After puberty responsible for male behavior, large SDN-POA present • Female Rats (low androgen levels) – After puberty Small SDN-POA (reversible with androgen treatment) – Lordosis (arching of back when sexually receptive)

Metabolism and Growth • Metabolism and Growth information: – Reader / Handout – Class Today – Discussion Today