Gametogenesis – Production of sperm & eggs
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings IB Assessment Statement Draw and label a diagram of a mature sperm and egg.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structure of Sperm Remember this is a single cell ~50 um long and 3 um wide at the 'head'. The 40 um tail is omitted from this diagram. The acrosome vesicle contains the enzymes required to digest its way though the ovum wall.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structure of Sperm Haploid nuclei (n=23) containing the paternal chromosome set The 'mid-section' of the sperm contains many mitochondria which synthesis ATP to provide the energy for the movement of the tails structure. Protein fibres add longitudinal rigidity and provide a mechanism of propulsion.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structure of mature secondary oocyte The haploid nuclei (arrested at prophase II ) sits inside a cell with a large volume of cytoplasm (yolk). During follicle development unequal division of the cell during meiosis produces the 1st polar body that can be seen outside the plasma membrane. This will not develop. The Zona pellucida surrounds the structure and is composed of glycoproteins. With the cortical granules they will be involved in the acrosome reaction at fertilisation. Around the outside are the follicular cells.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Gametogenesis Introduction Gametogenesis is the formation of gametes (sperm and egg cells) The process of gametogenesis is based on meiosis, but differs in females and males – Oogenesis is development of mature ova (egg) – Spermatogenesis is production of mature sperm
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gametogenesis Sequence 1.Multiplication phase – gamete cells reproduce by mitosis. The stage is repeated many times 2.Growth phase – gamete cells called primary spermatocytes grow and mature 3.Maturation phase -- Cells undergo meiosis and form haploid cells.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gametogenesis Sequence – Maturation Maturation phase -- Cells undergo meiosis and form haploid cells. The products of meiosis I are secondary spermocytes and secondary oocytes. Spermocytes are haploid cells formed in the seminiferous tubules of testes; that will develop in to sperm. Secondary oocytes are haploid cells derived from a primary oocyte shortly before ovulation in the ovary The products of meiosis II are spermatids(sperm) and ova (egg)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and Function of the Testis Spermatogenesis begins at puberty and continues throughout life. It is the production of sperm.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings IB Assessment Statement Annotate a light micrograph of testis tissue to show the location and function of interstitial cell (leydig cells), germinal epithelium cells, developing spermatozoa, and Sertoli cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Seminiferous Tubule of the Testis A.Spermazoas B.Spermatids C.Secondary spermatocytes D.Primary spermatocytes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings IB Assessment statement Outline the role of the epididymis seminal vesicle and prostate gland in the production of semen. spermatogenesis, including the number of gametes and the timing of the formation and release of gametes.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings IB Learning Objective Outline the role of the epididymis seminal vesicle and prostate gland in the production of semen Epididymis: testicle fluids are removed and the sperm concentrated sperm mature here and develop the ability to swim Seminal vesicles: adds nutrients that include fructose sugar for respiration mucus to protect sperm in the cell Prostate: adds fluids that neutralise the vaginal acids and minerals ions mineral ions
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Outline the processes involved in spermatogenesis within the testis, including mitosis, cell growth, the two divisions of meiosis and cell differentiation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and Function of the Testis Testis consists of many seminferous tubules. – These tubules are lined with germinal epithelial cells which divide repeatedly
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Seminferous tubules. – These tubules are also lined with nutritive cells (Sertoli Cells) Sertoli cells feed sperm producing cells (spermatocytes, secondary spermatocytes and spermatids) in the seminferous tubules.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and Function of the Testis – Between theses seminferous tubules is connective tissues that contain blood capillaries, with groups of interstitial cells These interstitial cells are hormone- secreting (endocrine gland)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Structure and Function of the Testis These semminiferous tubules in the testes the sperm drains into the epididymis. – The epididymis is a very coiled tube that leads to the sperm duct
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sequence of Mature Sperm Production Germinal epithelial cells of the seminiferous tubule undergo mitotic division and produce many diploid cells called primary spermatocytes. Primary spermatocytes undergo meiosis I and form haploid secondary spermatocytes.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sequence of Mature Sperm Production These haploid secondary spermatocytes undergo meiosis II and form spermatids These spermatids are supported by the serotoli cells Spermatids become mature sperm called spermatozoa.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings From spermatid to spermazoan (mature sperm)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sequence of Mature Sperm Production Spermatids move from the seminferous tubules into the epididymis. In the Epididymis, spermatids mature and become motile spermazoans The epididymis is a place where sperm is stored and where it completes it growth and development
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
These epididymis tubules drain into a system of channel which leads to the sperm ducts. It takes 20 days for the sperm to pass through these complicated epididymis tubules
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings During these 20 days they develop into motile strong cell with the ability to fertilize any egg. During ejaculation the sperm are propelled from the epididymis through the muscular vas deferens ( a tube that goes from the epididymis to the urethra).
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sperm are transported in a nutritive fluid secreted by glands, mainly the seminal vesicles and prostate gland. Semen is highly basic (alkaline) solution.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
From spermatid to spermazoan (mature sperm)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE Spermatogonium Primary spermatocyte (in prophase of meiosis I) Mitotic division, producing large numbers of spermatogonia Meiosis I completed Differentiation and onset of meiosis I Secondary spermatocyte Meiosis II Early spermatids Spermatids (at two stages of differentiation) Differentiation Sperm cells Neck Head Midpiece Tail Plasma membrane Mitochondria AcrosomeNucleus Sertoli cell nucleus Lumen of Seminiferous tubule Cross section of seminiferous tubule Testis Epididymis Seminiferous tubule
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Spermogenesis
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Spermarozoa
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings IB Learning Objective State the role of LH, testosterone and FSH in spermatogenesis.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Roles of Hormones in Spermatogenesis Puberty is triggered by the hypothalamus part of the brain. Hypothalamus stimulates the pituitary gland to produce and release FSH hormones and LH hormones. FSH (follicle-stimulating hormone) initiates sperm production LH (luteinising hormone) stimulates the endocrine cells of the testes to release progesterone.
LE Stimuli from other areas in the brain Anterior pituitary Hypothalamus Negative feedback Primary and secondary sex characteristics Leydig cells make testosterone LH Testis Sertoli cells Spermatogenesis FSH
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Roles of Hormones in Spermatogenesis Activity of testosterone is regulated by a negative feedback system. High testosterone levels suppress LH hormones stimulation. Low LH in blood reduce the release of testosterone.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Animation on Spermatogenesis student_view0/chapter28/animation__spermatoge nesis__quiz_1_.htmlhttp://highered.mcgrawhill.com/sites/ / student_view0/chapter28/animation__spermatoge nesis__quiz_1_.html cw/content/index.htmlhttp://wps.aw.com/bc_martini_eap_4/40/10469/ cw/content/index.html
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings IB LEARNING OBJECTIVE Annotate a diagram of the ovary to show the location and function of germinal epithelium, primary follicles, mature follicle and secondary oocyte.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
IB LEARNING OBJECTIVE Outline the processes involved in oogenesis within the ovary, including mitosis, cell growth, the two divisions of meiosis, the unequal division of cytoplasm and the degeneration of polar body..
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Oogenesis Oogenesis differs from spermatogenesis in three major ways: – During meiosis divisions, cytokinesis is unequal, with almost all of the cytoplasm in one daughter cell, the secondary oocyte
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Unlike sperm, eggs are not produced continuously throughout life – Oogenesis has long “resting” periods, whereas sperm are produced in uninterrupted sequence
LE Primary germ cell in embryo Mitotic division Primary oocyte Ovary Oogonium Differentiation Oogonium in ovary Primary oocyte within follicle Growing follicle Secondary oocyte Completion of meiosis I and onset of meiosis II Ovulation First polar body Mature follicle Entry of sperm triggers completion of meiosis II Second polar body Ovum Ruptured follicle Ovulated secondary oocyte Corpus luteum Degen- erating corpus luteum
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and function of ovaries In the female ovaries are about 3 cm long and 1.5 cm thick. Ovaries produce three important things 1.Egg Cells 2.Oestrogen Hormone 3.Progesterone Hormone
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and function of ovaries The outer layer of the ovary is lined by a germinal epithelium layer This germinal epithelium layer divides by mitosis and forms oogonium.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and function of ovaries These oogonium migrate to the connective tissue of ovary and continue to grow and mature and become primary oocytes The mature primary oocytes become surrounded by layers of follicle cell.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and function of ovaries The follicle cell and primary oocytes structure is called the primary follicle.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and function of ovaries Primary follicle divides via meiosis I and forms secondary oocyte.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and function of ovaries Secondary oocyte stays in prophase II of Meiosis II until arrival of sperm Secondary oocyte is released from follicle tissue in ovary a into oviduct. Follicle tissue in ovary become corpus luteum.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Process of Oogenesis
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and function of ovaries A pair of oviducts (fallopian tubes) extend from the ovaries to the uterus Oviducts are the site of fertilization
LE 46-15a From ovulation to implantation Cleavage starts Fertilization occurs Uterus Ovulation Ovary Endometrium The blastocyst implants Cleavage continues
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sequence of Oogenesis Begins in ovaries of the fetus before birth. Germ cells in the female embryo become oogonia (ovary –specific) stem cells. These oogonia become primary oocytes (2n) and remain within small follicles(folds) in the ovaries until puberty.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sequence of Oogenesis in a female’s life During puberty hormones cause these primary oocytes develop into via meiosis (1) secondary oocytes (n). These secondary oocytes are the final development of the oocytes. This secondary oocyte is release during ovulation, by the rupture of a follicle wall.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
OOGENESIS ANIMATIONS swf_maturation_of_.swfhttp://msjensen.cehd.umn.edu/1135/Links/animations/Flash/0044- swf_maturation_of_.swf hill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/ /63089/28_02_1.swf::Structure%20of%20the%20Ovary%20and %20the%20Developmental%20Sequence%20of%20the%20Ovarian% 20Follicleshttp://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/ /63089/28_02_1.swf::Structure%20of%20the%20Ovary%20and %20the%20Developmental%20Sequence%20of%20the%20Ovarian% 20Follicles ex.htmlhttp://wps.aw.com/bc_martini_eap_4/40/10469/ cw/content/ind ex.html
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings IB ASSESSMENT STATEMENT Compare the process of spermatogenesis and oogenesis, including number of gametes and the timing of the formation and release of gametes.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings OOGENESIS VS SPERMATOGENSIS
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
COMPARING OOGENESIS & SPERMATOGENSIS ANIMATIONS ex.htmlhttp://wps.aw.com/bc_martini_eap_4/40/10469/ cw/content/ind ex.html