DOCSLIB.ORG

Cell Division, Gametogenesis & Theory of Ovulation

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Cell Division, Gametogenesis & Theory of Ovulation CELL DIVISION, GAMETOGENESIS & THEORY OF OVULATION Cell Cycle • The cell cycle is the series of events that take place in the cell leading to its division and duplication that produces two daughter cells. • Periods of cell cycle: • Interphase • Cell division • Cytokinesis Interphase • It is also called the Interkinesis / Resting phase. • During this stage, the nucleus is not dividing but the DNA in the nucleus is duplicated in preparation for the next division. • Phases of interphase: • Gap 0 (G0) • Gap 1 (G1) • Synthesis (S) • Gap 2 (G2) • Gap 1(G1) • The cell grows and functions normally. • A high amount of protein synthesis occurs and the cell grows to double its original size. • More organelles are produced. • The volume of cytoplasm increases and mitochondria and chloroplasts divide. • If the cell is not to divide again, it will enter G0. • Synthesis (S) • The cell duplicates its DNA. • This is also known as The Swanson Phase. • Gap 2 (G2) • The cell resumes its growth in preparation for division. • Gap Zero (G0) • Some cells do not further divided means their cell cycle is arrested so it is termed as Gap Zero (G0). Cell Division • Cell division is the process by which a parent cell divides into two or more daughter cells. • Eukaryotes undergo two type of cell division : • Mitotis • Meiosis • Prokaryotes undergo cell division : • Binary fission Mitosis (Karyokinesis) • It is the process in which the parental cell divides into two daughter cells which are genetically identical to the parent cell. • All somatic (body) cells multiply by the mitosis cell division. • Stages of Mitosis: 1. Prophase 2. Prometaphase 3. Metaphase 4. Anaphase 5. Telophase Prophase • This process is also called as Chromatin condensation. • The chromatin condenses into double rod-shaped structures (chromosomes). • Centrioles move to the opposite sides of the nucleus. • Nucleolus disappears. • Nuclear membrane disintegrates. Prometaphase • It is the phase of mitosis following prophase and preceding metaphase. • Kinetochore (the protein structure) on chromatids where the spindle fibers attach, during cell division to pull sister chromatids apart. Metaphase • Chromosomes meet in the middle. • Chromosomes arrange at equator of cell. • Become attached to spindle fibers by centromeres. • Homologous chromosomes do not associate. Anaphase • Chromosomes get pulled apart. • Spindle fibers contract pulling chromatids to the opposite poles of the cell. Telophase • Chromosomes uncoil. • Spindle fibres disintegrate. • Centrioles replicate. • Nuclear membrane forms. • Cell divides. Cytokinesis • Cytokinesis begins shortly after the onset of sister chromatid separation in the anaphase of mitosis. • In this stage of cell division, there is invagination of cell wall at the equator toward the center of the parental cell which results into equal division of the cytoplasm and two daughter cells are formed. • After cytokinesis, each daughter cell is in the interphase portion of the cell cycle. Meiosis • During this cell division, a nucleus divides into four daughter nuclei having half of the chromosome number to the parent nucleus. • Gametes (sex cells) divided by this type of cell division. • Stages of meiosis: 1) Meiosis I 2) Meiosis II Meiosis I • Meiosis I segregates homologous chromosomes, producing two haploid cells from a diploid cell, so it is referred to as a Reduction division. • Phases of Meiosis I : 1. Prophase I a) Leptotene b) Zygotene c) Pachytene d) Diplotene e) Diakinesis 2. Metaphase I 3. Anaphase I 4. Telophase I Prophase I • Prophase I is the longest phase of meiosis. • During prophase I, DNA is exchanged between homologous chromosomes in a process called Homologous Recombination. • It can be subdivided into; • Leptotene • Zygotene • Pachytene • Diplotene • Diakinesis Leptotene(Leptonema) • Greek words meaning "Thin threads". • Leptotene is of very short duration. • During this phase the chromosomes become visible. • Progressive condensation and coiling of chromosome fibers takes place. Zygotene(Zygonema) • Greek words meaning "Paired threads“. • chromosomes line up with each other into homologous chromosome pairs. • Pairing is brought about in a zipper-like fashion and may start at the centromere (Procentric) or at the chromosome ends (Proterminal) or at any other portion (Intermediate). • The paired chromosomes are called Bivalent Or Tetrad Chromosomes. Pachytene(Pachynema) • Greek words meaning "Thick threads“. • At this point a tetrad of the chromosomes has formed known as a bivalent. • Here chromosomal crossover occurs called as Crossing Over. • Nonsister chromatids of homologous chromosomes may exchange segments over regions of homology. • At this site they become attached, this point is called as Chiasmata. Diplotene(Diplonema) • Greek words meaning "Two threads“. • In mammalian and human fetal oogenesis all developing oocytes develop to this stage and are arrested before birth. • This suspended state is referred to as the Dictyotene Stage or Dictyate. • • It lasts until meiosis is resumed to prepare the oocyte for ovulation, which happens at puberty or even later. Diakinesis • Greek words meaning "Moving through". • This is the first point in meiosis where the four parts of the tetrads are actually visible. • Sites of crossing over entangle together, effectively overlapping, making chiasmata clearly visible. • Other than this observation, the rest of the stage closely resembles prophase of mitosis; the nucleoli disappear, the nuclear membrane disintegrates into vesicles, and the meiotic spindle begins to form. Metaphase I • The nuclear membrane disappears. • Spindle is formed as in mitosis. • Chromosomes are attached by centromeres. • Bivalents gather on metaphase plate. Anaphase I • Differs from that in mitosis. There is no splitting of the centromeres. • One entire chromosome of each pair moves to each pole of the spindle. • The resulting daughter cells therefore have half chromosomes, each made up of 2 chromatids. Telophase I • Karyokinesis takes place or without it cell enters in 2nd division of meiosis, which is similar to mitosis. • Cells may enter a period of rest known as Interkinesis or Interphase II. Meiosis II • Also known as Equational division. • Mechanically, the process is similar to mitosis, though its genetic results are fundamentally different. • The end result is production of four haploid cells from the two haploid cells, produced in Meiosis I. Phases of Meiosis II 1. Prophase II 2. Metaphase II 3. Anaphase II 4. Telophase II Prophase II • The disappearance of the nucleoli and the nuclear envelope. • The shortening and thickening of the chromatids. • Centrosomes move to the polar regions and arrange spindle fibers for the second meiotic division. Metaphase II • The centromeres contain kinetochores that attach to spindle fibers from the centrosomes at opposite poles. Anaphase II • Chromosomes get pulled apart. • Spindle fibers contract pulling chromatids to the opposite poles of the cell. Telophase II • It is marked by decondensation and lengthening of the chromosomes. • The disassembly of the spindle occurs. • Nuclear envelopes reform and cleavage or cell wall formation eventually produces a total of four daughter cells. • Meiosis is now complete and ends up with four new daughter cells. Gametogenesis • Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. • Animals produce gametes directly through meiosis in organs called gonads (testicle in males and ovary in females). • Males and females of a species that reproduces sexually have different forms of gametogenesis. Spermatogenesis (In male) oogenesis (In female) Spermatogenesis • Spermatogenesis is the process in which spermatozoa are produced from male primordial germ cells by way of mitosis and meiosis. • It comprises: i. Spermatocytogenesis- Process of formation of Spermatocyte from Spermatogonium. ii. Spermiogenesis(Metamorphosis)- Process of transformation of Spermatids into Spermatozoa. • A Spermatogonium is an undifferentiated male germ cell, originating in a seminiferous tubule and dividing into two primary spermatocytes in the production of spermatozoa. • There are three subtypes: Type A(d) cells (with dark nuclei): These cells replicate to ensure a constant supply of spermatogonia to fuel spermatogenesis. Type A(p) cells (with pale nuclei): These cells divide by mitosis to produce Type B cells. Type B cells: which divide to give rise to Primary spermatocytes. • Each Primary Spermatocyte duplicates its DNA and subsequently undergoes meiosis I to produce two haploid Secondary Spermatocytes. • Each of the two Secondary Spermatocytes further undergo meiosis II to produce two Spermatids (haploid). • So 1 primary spermatocyte => 4 spermatids. • The process of spermatogenesis is divided into the following phases • Multiplication phase • Growth phase • Maturation phase • Metamorphosis of spermatid Multiplication phase • Also known as Spermatocytogenesis. • The sperm mother cells present in the germinal epithelium of the seminiferous tubules divide repeatedly by mitosis to form large number of diploid rounded sperm mother cells which are called as spermatogonia. • Some of these sex cells move towards the lumen of seminiferous tubules and enter the growth phase. These cells are called primary spermatocytes. • The primary spermatocytes are diploid and contain chromosomes. • Some of the sex cells produced by the division of spermatogonia remain in their original condition
Load more

Recommended publications
  • The Reproductive System
    The Wiltshire School of Beauty and Holistic Therapy Certificate of Merit in Anatomy and Physiology W: www.wsbht.co.uk E: [email protected] T: 07824 337333 The Wiltshire School of Beauty and Holistic Therapy Certificate of Merit in Anatomy and Physiology© Certificate of Merit in Anatomy and Physiology Lesson 6: The Urinary And Reproductive System The Wiltshire School of Beauty and Holistic Therapy Certificate of Merit in Anatomy and Physiology© The Urinary System The urinary system is made up of the kidneys, ureters, bladder and urethra and is responsible for controlling the amount of water and salts that are absorbed and filtered into the blood, and will regulate the chemical composition of body fluids by removing metabolic waste. The Kidneys These are two bean shaped kidneys in the body, one on either side, located near the middle of the back behind the 13th rib. These 5 – 6 inch long organs are responsible for processing waste products and filtering the blood to ensure that the body is in a state of balance. The waste comes from the normal breakdown from the food that is eaten. The Wiltshire School of Beauty and Holistic Therapy Certificate of Merit in Anatomy and Physiology© It is essential that this waste is removed as it could damage the body. Each kidney is joined to the aorta, which is the largest artery in the body by a short renal artery, as they receive a huge blood supply. Each kidney contains around a million nephrons, a tube which is closed at one end, and open at the other.
    [Show full text]
  • Fr. Ryan 'Human Sexuality' I Supplement (Portions)
    THEOLOGY I HUMAN SEXUALITY SUPPLEMENT This collection of supplementary materials, in this format or any other, is the property of Father Ryan High School, and should not be reprinted or distributed without the express permission of the Administration of Father Ryan High School. FEMALE PHYSIOLOGY EXTERNAL GENITALIA AND SECONDARY SEX CHARACTERISTICS PUBIC HAIR: A triangular mass of hair covering the mons pubis. The amount of and thickness of the pubic hair varies from person to person. MONS PUBIS: A fatty pad at the top of the vulva; covered with pubic hair and susceptible to sexual stimulus. VULVA: The word comes from the Latin root “covering”. The vulva is not one specific organ, but a collection of genital structures. OUTER LIPS (Labia Majora) a. The outermost hair-covered folds of skin surrounding the genitals. b. They vary greatly in size. c. Like the scrotum, the outer lips swell slightly with stimulation; in their stimulated state they pull back and expose the Inner Lips. INNER LIPS (Labia Minora) a) This is the second covering of the vaginal opening; they enclose the vaginal and urethral opening. b) They are a thin, moist, sensitive fold of skin containing many erotic nerve endings and blood vessels. c) They contain the same tissue as the shaft of the penis; as a result they too swell with sexual stimulus. CLITORIS a) This is the most sexually sensitive part of the female body. It corresponds to the glans or head of the penis. b) Though there is no reproductive purpose, the clitoris is made of erectile tissue and contains a high concentration of erotic neural receptors and blood vessels.
    [Show full text]
  • Embryo Adoption
    EMBRYO ADOPTION Reproductive Technology, In-Vitro Fertilization, and Whether Christians Should Adopt Embryos 1. Define Terms 2. Statistics/History 3. Public Policy 4. Most importantly – Search the Scriptures 5. Christian Ethics 6. Pastoral Care and Practice 7. Questions, Comments, Concerns, Discussion WHY? “Reproductive Technology encompasses all current and anticipated uses of technology in human and animal reproduction, including assisted reproductive technology, contraception and others.” TERMS: REPRODUCTIVE TECHNOLOGY Assisted Reproductive Technology treats infertility and includes: Artificial insemination Cloning Cytoplasmic Transfer Cryopreservation of sperm, oocytes, embryos Embryo transfer Fertility medication Hormone treatment In Vitro Fertilization In Vitro generated gametes Preimplantation genetic diagnosis TERMS: ASSISTED REPRODUCTIVE TECHNOLOGY “Future chances of pregnancy, facilitating an informed choice of family planning” Mapping a woman’s ovarian reserve, follicular dynamics, and associated biomarkers Semen analysis TERMS: PROGNOSTICS “A form of reproductive technology that enables people to control their fertility” TERMS: CONTRACEPTION Artificial wombs: “at the developmental stage” Germinal choice technology = genetic screening of blastocysts (early embryos), or germline engineering (human genetic engineering used to alter genes in the first cells of the blastocyst) In Vitro Parthenogenesis = sperm triggers the development of the egg cell into an embryo but makes no genetic contribution to the
    [Show full text]
  • Further Reading
    1 HYPOTHALAMUS PITUITARY GONADAL AXIS Lecture One Further Reading Female Menstrual Cycle (the cycle will be discussed in the next lecture, in a somewhat less detailed manner) - The primary female reproductive organ are the ovaries, an almond-shaped organ in the lower abdomen. - The ovaries produce eggs or the ovum, the functional unit of the ovaries are the follicles. Females are born with immature follicles called “primordial follicles”, a follicle of this type consists of a primary oocyte (an immature ovum), surrounded by a relatively flat layer of epithelium, these epithelial cells are known as “granulosa cells”. - Follicles remain immature in the primordial stage throughout childhood, but then suddenly are triggered into maturity during puberty due to the sudden rise in GnRH (GnRH secretion remains low throughout childhood but increases in late childhood to trigger puberty) with subsequent rise in FSH and LH. - Puberty immediately triggers the the menstrual cycle, which lasts for 28 days monthly, and are divided into two subcycles, an ovarian cycle (which we will discuss), and a uterine cycle (discussed in lecture three, involves menstrual blood). However these cycles occur simultaneously, don’t worry, all will be clear by the next lecture. - Ovulation occurs at day 14 of this cycle. (all days mentioned subsequently are approximations) - Usually only 6-12 follicles participate in menstrual cycles, with only one follicle releasing its ovum to be fertilized. - The ovaries contain around 300-500 thousand follicles, 6-12 of which are usually responsive to participate in the menstrual cycle each month, with only one follicle releasing its ovum and the remaining follicles simply degenerate.
    [Show full text]
  • Family Law—Egg Donation and Stem Cell Research—Eggs for Sale: the Scrambled State of Legislation in the Human Egg Market
    University of Arkansas at Little Rock Law Review Volume 35 Issue 1 Article 7 2012 Family Law—Egg Donation and Stem Cell Research—Eggs for Sale: The Scrambled State of Legislation in the Human Egg Market Kitty L. Cone Follow this and additional works at: https://lawrepository.ualr.edu/lawreview Part of the Family Law Commons, Health Law and Policy Commons, and the Science and Technology Law Commons Recommended Citation Kitty L. Cone, Family Law—Egg Donation and Stem Cell Research—Eggs for Sale: The Scrambled State of Legislation in the Human Egg Market, 35 U. ARK. LITTLE ROCK L. REV. 189 (2012). Available at: https://lawrepository.ualr.edu/lawreview/vol35/iss1/7 This Note is brought to you for free and open access by Bowen Law Repository: Scholarship & Archives. It has been accepted for inclusion in University of Arkansas at Little Rock Law Review by an authorized editor of Bowen Law Repository: Scholarship & Archives. For more information, please contact [email protected]. FAMILY LAW—EGG DONATION AND STEM CELL RESEARCH—EGGS FOR SALE: THE SCRAMBLED STATE OF LEGISLATION IN THE HUMAN EGG MARKET I. INTRODUCTION The world has seen the rapid rise of numerous medical technologies that were outside the realm of possibility just a few decades ago.1 These developing technologies, although generally providing incredible enhance- ment to our lives, have also created an equally incredible legal tangle.2 Cou- ples who would never have had children in earlier times are now able to reproduce with the help of science—and a host of doctors, donors, and
    [Show full text]
  • Unit 4 Lecture 12
    Unit 4 Lecture 12 Unit 4 Lecture 12 THE REPRODUCTIVE SYSTEM Reproduction is the process by which a species continues to survive. Genetic material is passed from one generation to the next through sexual reproduction. Offspring have a combination of genes from both patents. The primary reproductive organs are called gonads because they produce gametes (sperm cells in the male and ova in the female). Gonads also produce hormones. In addition to the primary sex organs are the secondary sex organs which transport, store the gametes, and accessory glands that produce materials that support the gametes. Male Reproductive System The function of the male reproductive system is to produce the sex steroid testosterone, to produce sperm (process is called spermatogenesis), and to deliver sperm to the female vagina. The testes (testicles) are a pair of oval glands located in the scrotum and are divided into 200-300 compartments called lobules by the tunica albuginea. Each tubule contains 1-3 seminiferous tubules. The seminiferous tubules produce: sperm cells, sustentacular (Sertoli) cells that support, protect, and nourish sperm cells and secrete inhibin (a hormone that helps regulate sperm production by inhibiting FSH), and Interstitial cells (cells of Leydig) which secrete testosterone. Spermatogenesis is an ongoing process by which sperm are made and the chromosome number is reduced to (n) or the haploid number of chromosomes. Humans have 23 pairs or 46 chromosomes. Twenty-two pairs are homologous and are called autosomes. One pair (XY) is called the sex chromosomes and this chromosome determines the sex of the individual. Any individual having a Y chromosome is considered male.
    [Show full text]
  • INTRODUCTION to EMBRYOLOGY Foundation Block - Lecture 1
    Editing file INTRODUCTION TO EMBRYOLOGY Foundation Block - Lecture 1 important & Doctor’s notes Extra information Objectives : ❖ Define Embryology. ❖ Define the developmental periods. ❖ Define the significance of embryology. ❖ Define the different embryological terminology. ❖ Define the nomenclature used to describe body parts, positions and relationships. ❖ Describe in brief the important events in embryology. Definition development (ﻗﺑل اﻟوﻻدة)Embryology refers to the prenatal of embryos and fetuses Human embryology is the science Importance concerned with the origin and development of a human being from a zygote to birth of an infant. ● The study of prenatal stages of development, especially those occurring during the Development does not stop at birth. Important embryonic period helps us understand the changes in addition to growth occur after birth normal body structure and the cause of (postnatal changes) e.g. development of teeth .(ﻋﯾوب ﺧﻠﻘﯾﺔ) congenital anomalies and female breasts .. ● So, It concerned with various genetic and /or environmental factors that disturb normal development and produce birth defect. 3 Developmental periods Prenatal development: Postnatal development: Includes the main developmental Includes changes occurring Then changes occuring before birth after birth. e.g. teeth and (from zygote to before birth), breast. and is divided into 2 periods NOTE: ● Prenatal development is more rapid than postnatal development and results Embryonic period: Fetal period: in more striking changes. Begins at fertilization Begins at the beginning of ● The most critical period is and ends with the end of the 9th week and ends at the embryonic period. the 8th week. birth. (called an embryo ) (called a fetus) 4 Critical Period Of Human Development ● It is the stage of development of an embryo that is susceptible to an agent, such as a drug or virus, which can lead to congenital abnormalities.
    [Show full text]
  • SSIP – January 2020 SUBJECT: LIFE SCIENCES Participant's Guide
    SSIP – January 2020 SUBJECT: LIFE SCIENCES Participant’s Guide 1 © COPYRIGHT This work is protected by the Copyright Act 98 of 1978. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without permission in writing from Matthew Goniwe School of Leadership and Governance. Whilst every effort has been made to ensure that the information published in this work is accurate, Matthew Goniwe School of Leadership and Governance takes no responsibility for any loss or damage suffered by any person as a result of the reliance upon the information contained therein. 2 Table of contents Page A Foreword 4 B Purpose 4 C Overall SSIP purpose/goals 4 D Programme outcomes 4 E Learning assumed to be in place 4 F Target audience 5 G Notional hours 5 H Course design and assessment strategy 5 Annual teaching plan (ATP) 8 Cognitive demand levels in Life Sciences 10 Course timetable 12 Module 1: DNA and Protein synthesis 16 Module 2: Meiosis 40 Module 3: Reproductive strategies in Vertebrates 61 Module 4: Reproduction in humans 76 3 A. FOREWORD This Just in Time teacher training workshop is organized at the start of term 1. All topics to be covered in term 1 by the gr.12 teacher will be mediated to enable teachers to unlock the content for the learners. The dates for the workshops were announced in 2019 at a joint meeting with Matthew Goniwe School of Leadership and Governance (MGSLG) and Teacher Development (TD).
    [Show full text]
  • Could the P75 Neurotrophin Receptor P75ntr Help Unlock the Mysteries of Infertility?
    Eastern Kentucky University Encompass Honors Theses Student Scholarship Fall 2020 Could the p75 Neurotrophin Receptor p75NTR Help Unlock the Mysteries of Infertility? Mayci Fullmer [email protected] Follow this and additional works at: https://encompass.eku.edu/honors_theses Recommended Citation Fullmer, Mayci, "Could the p75 Neurotrophin Receptor p75NTR Help Unlock the Mysteries of Infertility?" (2020). Honors Theses. 792. https://encompass.eku.edu/honors_theses/792 This Open Access Thesis is brought to you for free and open access by the Student Scholarship at Encompass. It has been accepted for inclusion in Honors Theses by an authorized administrator of Encompass. For more information, please contact [email protected]. EASTERN KENTUCKY UNIVERSITY Could the p75 Neurotrophin Receptor p75NTR Help Unlock the Mysteries of Infertility? Honors Thesis Submitted In Partial Fulfillment Of The Requirements of HON 420 Fall 2020 By Mayci Fullmer Faculty Mentor Dr. Oliver Oakley Department of Biological Sciences ii Could the p75 Neurotrophin Receptor p75NTR Help Unlock the Mysteries of Infertility? Mayci Fullmer Dr. Oliver Oakley, Department of Biological Sciences Abstract Histology is the study of microscopic tissue structures that examines the correlation between structure and function. This technique was utilized when analyzing the biological processes of folliculogenesis and oogenesis. These processes study the maturation of the ovarian follicle and production of an ovum, respectively. The p75 neurotrophin receptor (p75NTR) has been identified to contribute to the maturation of ovarian follicles, but the role of p75NTR in ovulation remains unknown. To investigate the role of p75NTR in ovulation, an animal study analyzing the histology of the mouse ovary was conducted.
    [Show full text]
  • Lecture Outline
    Biology 218 – Human Anatomy RIDDELL Chapter 27 Adapted form Tortora 10th ed. LECTURE OUTLINE A. Introduction (p. 835) 1. Sexual reproduction is the process by which organisms produce offspring by means of germ cells called gametes; when a male gamete unites with a female gamete during fertilization, the resulting cell contains one set of chromosomes from each parent. 2. The organs of the reproductive systems may be grouped by function: i. gonads produce gametes and secrete sex hormones a. testes produce sperm cells b. ovaries produce ova ii. ducts receive, store, and transport gametes iii. accessory sex glands produce substances that protect gametes and facilitate their movement iv. supporting structures assist delivery and joining of gametes and, in females, the growth of the fetus during pregnancy 3. Gynecology is the medical specialty concerned with diagnosis and treatment of diseases of the female reproductive system; although urology is the study of the urinary system, urologists also diagnose and treat diseases and disorders of the male reproductive system. B. Male Reproductive System (p. 836) 1. The male reproductive system includes: i. testes (male gonads), which produce sperm and secrete hormones ii. system of ducts, which stores and transports sperm to the exterior iii. accessory sex glands, which produce secretions that mix with sperm to form semen iv. supporting structures including the scrotum and penis 2. Scrotum: (p. 836) i. the scrotum is an outpouching of the abdominal wall consisting of loose skin and superficial fascia that hangs from the root of the penis ii. externally, it has a median ridge called a raphe which separates the pouch into two lateral portions iii.
    [Show full text]
  • Human Reproductive System
    Human Reproductive System 1 Netter’s, et al, Images used under Fair Use Copyright Practice for Educational Purposes. DISCLAIMER! • This lecture is a clinically and scientifically frank ADULT discussion about the human reproductive system with ADULT students who are studying to go into fields of health care and need a fundamental knowledge of: – The anatomy and physiology of the human reproductive system, – Elementary concepts of anatomy, physiology and biochemistry of sexual intercourse, and – Embryogenesis, fetal development, gestation and delivery of the human fetus. • If you feel uncomfortable with and/or about this[these] topic[s], it is quite likely that you’re probably not going into an appropriate field of study for your future and may wish to reconsider your career path. You’ve been forewarned. 2 Perineal Musculature – Compare and Contrast – Male and Female • This graphic simply reinforces that which you learned in the chapter on muscles and illustrates some orientation of organs with vessels and other anatomical landmarks. 3 Male Reproductive System • The penis is the organ of copulation and is an accessory organ. • The reproductive organs in the male are the testes. • The dartos is involuntary muscle that puts the wrinkles in the scrotum; remember the cremaster is the muscle that lifts the testes towards the body or lowers them from the body. • The epididymis is 4-6 meters in length and is where spermiogenesis (sperm maturation) occurs. • It takes sperm about 12 days to traverse the epididymis. • Spermatogenesis (production of sperm) takes place, specifically, in the seminiferous tubules. • The testes produce the sperm and secrete testosterone.
    [Show full text]
  • Dition Is That of Early Development-Ie, of Quasi-Immature Growth-And
    "LEPROSY AND HEREDITY." 123 the part of the ovum which decides the sex of the resulting others by a fund raised by the local residents. The dog was embryo....... The embryo pursues for a time a straight destroyed by its owner, and on a post-mortem examination path, then deviates to the male or female side." What being made by Dr. Barron of Liverpool and Mr. Welsh, the determines its deviation ? Which is the straighter path ? veterinary surgeon of the district, it was found to be the I do not agree with Mr. Wilson that "the impetus to subject of rabies The same dog also attacked Dr. Harvey of this deviation is given at the commencement of its existence Wavertree, but fortunately the bite of the animal did not as a fertilised ovum": it is further back. "The longer penetrate his clothes. A hurried meeting of the magistrates. fertilisation is delayed after its extrusion from the ovary the was convened on Saturday, and a muzzling order for the greater likelihood is there of the ovum developing into a whole district of West Derby was issued. female embryo, and vice tersa." It is this theory, built upon The Confinement of Inebriates. the devitalisation of the ovum menstruation, that I through I A instance of the for the more- wish to combat. melancholy necessity effectual dealing with confirmed inebriates was disclosed at the Premising that Mr. Wilson’s facts are true, which have coroner’s court on the 6th inst. The deceased, a married been corroborated by other observers, that conception city woman, had for years been so addicted to drink that she.
    [Show full text]