Ch. 26 Reproduction System

Question 1

Introduction

Answer 1

• sexual reproduction is when organisms produce offspring through union of germ cells called gametes
• after male gamete unites with female gamete an event called fertilization
• resulting cell contains one set of chromosomes from each parent
• males and females have anatomically distinct reproductive organs
• male and female reproductive organs are called gonads
• testes and ovaries produce gametes and secrete sex hormones

Question 2

Reproductive Systems

Answer 2

male- testes- gametes- sperms- testosterone
female- ovary- gametes- oocytes- estrogen and progesterone
* sex hormones affect maturation, development, and changes in activity of reproductive system organs

Question 3

Male Reproductive System

Answer 3

• organs of male include testes, system of ducts, accessory sex glands (seminal vesicles, prostate, bulbourethral glands), and several supporting structures, including scrotum and penis
• testes produce sperm and secrete hormones
• duct system transports and stores sperm, assists in their maturation, and conveys them to the exterior
• semen contains sperm plus secretions provided by the accessory sex glands
• penis delivers sperm into female reproductive tract and scrotum supports the testes

Question 4

Anatomy of Scrotum

Answer 4

• consists of loose skin and underlying subcutaneous layer that hangs from root of penis
• externally, single pouch of skin separated into lateral portion by a median ridge called Raphe
• internally, scrotal septum divides the scrotum into two sacs
• septum is made up of a subcutaneous layer of muscle tissue called dartos muscle
• cremaster muscle is a series of small bands of skeletal muscle that descend through the spermatic cord to surround the testis

Question 5

Internal and External Anatomy of Testes

Answer 5

testis:

1. interstital (Leydig’s) cells: testosterone
2. Seminiferorus tubules: spermatogenesis
3. Sertolic cells: support and nourish the sperms

Question 6

Sertoli Cells

Answer 6

• sustentacular cells are joined by tight junctions to one another
• form blood-testis barrier
• sertoli cells support, protect, and nourish spermatocytes, spermatids and sperm
• phagocytize excess spermatid cytoplasm; control movements of spermatogenic cells and release of sperm into lumen of seminiferous tubule
• produce fluid for sperm transport, secrete the hormone inhibin, which decreases the rate of spermatogenesis, and regulate the effects of testosterone and FSH

Question 7

Leydig Cell

Answer 7

• interstital cells secrete testosterone, most important androgen
• an androgen promotes development of masculine characteristics
• testosterone also promotes a man’s libido

Question 8

Spermatogensis

Answer 8

• spermatogenesis takes about 65-75 days
• spermatogonia, diploid chromosome number
• undergoes mitosis in seminiferous tubule
• rest of cells lose contact with basement membrane, squeee through tight junctions of blood-testis barrier, undergo developmental changes, and differentiate into primary spermatocytes
• primary spermotocytes are diploid (2n); they have 46 chromosomes
• primary spermatocytes replicated its DNA and meiosis begins
• meosis 1: homologous pairs of chromosomes line up at the metaphase plate, and crossing-over occurs
• meiotic spindle pulls one (duplicated) chromosome of each pair to an opposite pole of dividing cell

Question 9

Spermiogenesis

Answer 9

• maturation of haploid spermatids into sperm
• no cell division occurs in spermiogenesis, each spermatid develops into a single sperm cell
• spherical spermatids transform into elongated, slender sperm
• acrosome forms atop the condensing and elongating nucleus a flagellum develops, and mitochondria multiply
• sertoli cells dispose of excess ctyoplasm that is sloughed off during this process
• finally, sperm are released from their connections to sertoli cells an event known as spermiation
• sperm then enter the lumen of the seminiferious tubule
• fluid secreted by Sertoli cells pushes sperm along their way, toward the ducts of the testes, at this point sperm are not yet able to swim

Question 10

Ductus of the Testis

Answer 10

• pressure generated by the fluid secreted by Sertoli cells pushes sperm and fluid along the lumen of seminiferious tubules and then into a series of very short ducts called straight tubules
• straight tubules lead to a network of ducts in the testis called rete testis
• from rete testis, sperm move into a series of coiled efferent ducts in the epididymis that empty into a single tube called the ductus epididymis measure
• tail of the epidiidymis continues as the ductus (vas) deferens
• lined with pseudostratified columnar epithelium and encircled by a layer of smooth muscle; free surfaces of the columnar cells contain stereocili, long, branching microvilli that increase surface area for reabsorption of degenerated sperm
• epididymis is the site of sperm maturation, occurs over a period of about 14 days

Question 11

Ductus Deferens

Answer 11

• ductus epididymis becomes less convoluted, and its diameter increases; referred to as the ductus deferens or vas deferens
• ductus deferens, passes through the spermatic through the inguinal canal to enter the pelvic cavity; there it loops over the ureter and passes over the side and down the posterior surface of the urinary bladder
• dilated terminal portion of the ductus deferens is known as the ampulla
• functionally, the ductus deferens conveys sperm during sexual arousal from the epididymis toward the urethra by peristaltic contractions of its muscular coat
• ductus deferens also can store sperm for several months

Question 12

Ejaculatory Ducts

Answer 12

• formed by union of the duct from the seminal vesicle and the ampulla of the ducts (vas) deferens
• terminate in prostatic urethra, where they eject sperm and seminal vesicle secreations just before the release of semen from the urethra to the exterior
• urethra: males- shared terminal duct of the reproductive and urinary systems (passageway for both semen and urine)
• passes through prostate, deep muscles of the perineum, and penis and is subdivided into 3 parts
• prostatic urethra, membranous (intermediate) urethra and the spongy (penile) urethra
• spongy urethra ends at the external urethral oriface

Question 13

Seminal Vessicles

Answer 13

• seminal glands are posterior to and at the base of the urinary bladder anterior to the rectum
• secrete alkaline, viscous fluid that contains fructose, prostaglandins, and clotting proteins
• alkaline nature of the fluid helps to neutralize the acidic environment of the male urethra and female reproductive tract
• fructose- used for the production of ATP by sperm
• prostaglandins: contribute to sperm motility and viability and may also stimulate muscular contractions within the female reproductive tract
• clotting proteins help semen coagulate after ejaculation

Question 14

Bulbourethral Glands

Answer 14

• paired bulbourethral gland, or Cowper’s gland, lie inferior to prostate on either side of the membranous urethra within deep muscles of the perineum; ducts open into the spongy urethra
• during sexual arousal, the bulbourethral glands secrete an alkaline substances that protects the passing sperm by neutralizing acids from urine in the urethra
• at the same time, they secrete mucus that lubricates the end of the penis and the lining of the urethra, thereby decreasing the number of sperm damaged during ejaculation

Question 15

Prostate

Answer 15

• single gland, inferior to the urinary bladder and surrounds the prostatic urethra
• prostate secretes milkly, slightly acidic fluid that contains several sustances
  1. citric acid in prostatic fluid is used by sperm for ATP production
  2. Several proteolytic enzymes: prostate-specific antigen (PSA), pepsinogen, lysozyme, amylase, and hyaluronidase, eventually break down the clotting proteins from the seminal vesicles
  3. function of the acid phosphatase secreted by the prostate is unkown
  4. seminal plasmin in prostatic fluid is an antiboitic that can destroy bacteria; seminal plasmin may help decrease the number of naturally occuring bacteria in semen and in lower female reproductive tract
• secretions of the prostate enter the prostatic urethra through many prostatic ducts
• prostatic secretions make up about 25% of the volume of semen and contribute to sperm mobility and viability

Question 16

Parts of Sperm and Semen

Answer 16

• semen is a mixture of sperm and seminal fluid, liquid that consists of the secretions of the seminiferous tubules, seminal vesicles, prostate, and bulbourethral glands
• male whose sperm count falls below 20 million/mL is likely to be infertile
• prostatic secretion gives semen a milky appearance and fluids from seminal vesicles and bulbourethral glands give it a sticky consistency
• seminal fluid provides sperm with a transportation medium, nutrients, and protection from hostile acidic environment of male’s urethra and female’s vagina

Question 17

Penis

Answer 17

• contains urethra and is a passageway for the ejaculation of semen and excretion of urine
• body of penis is composed of 3 cyndrical masses of tissue, each surrounded by fibrous tissue called tunica albuginea
• 2 dorsolateral masses called corpora cavernose
• smaller midventral mass, corpus spongiosum, penis contains spongy urethra and keeps it open during ejaculation
• ski and a subcutaneous layer enclose all three masses; consists of erectile tissue

Question 18

Functions of Reproductive System

Answer 18

• produce ova
• secrete sex hormones
• recieve spermatoza
• provide sites for fertilization and implantation of blastocyst
• development of embryo and fetus
• facilitate parturition
• provide nourishment for baby

Question 19

Ovaries

Answer 19

• paired glands; female gonads and homologous to the testes
• series of ligaments hold them in position; broad ligament is part of the parietal peritoneum, attaches to the ovaries by a double-layered fold of peritoneum called mesovarium
• ovarian ligament anchors the ovaries to the uterus
• suspensory ligament attaches the ovaries to the pelvic wall
• each ovary contains a hilum, point of entrance and exit for blood vessels and nerves along which the mesovarium is attached

Question 20

Parts of Ovaries

Answer 20

• each ovary consists of:
• germinal epithelium is a layer of simple epithelium that covers surface of ovary
• mesothelium that covers the mesovarium
• tunics albuginea is whitish capsule of dense, irregular connective tissue immediately deep to the germinal epithelium
• ovarian cortex consists of ovarian follicles surrounded by dense irregular connective tissue that contains collagen fibers and fibroblast cells called stromal cells
• ovarian medulla is deep to ovarian cortex; consists of more loosely arranged connective tissue and contains blood vessel, lymphatic vessels and nerves

Question 21

Ovarian Follicles

Answer 21

• located in ovarian cortex and consist of oocytse in various stages of development plus cells surrounding them
• surrounding cells form a single layer they are called follicular cells; later in development when they form several ayers they are called granulosa cells
• surrounding cells nourish developing oocyte and begin to secrete estrogens as the follicle grows larger
• mature (graafian) follicle is large, fluid-filled follicle that is ready to rupture and expel its secondary oocyte, process known as ovulation
• corpus luteum contains the remnants of a mature follicle after ovulation; corpus luteum produces progesterone, estrogens, relaxin and inhibin until it degenerates into fibrous scare tissue called corpus albicans

Question 22

oogenesis

Answer 22

• formation of gametes in ovaries; oogenesis begins in females before they are even born
• before birth meiosis takes place and resulting germ cells undergo maturation
• during early fetal development, primitive germ cells migrate from yolk sac to the ovaries; germ cells differentiate within the ovaries into oogonia
• oogonia are diploid stem cells that divide mitotically to produce millions of germ cells
• before birth, most of these germ cells degenerate in a process known as astresia
• few develop into larger cells called primary oocytes that enter prophase of meosis 1 during fetal development but do not complete that phase until after puberty

Question 23

Follicular Development

Answer 23

• during arrested stage of development, each primary oocyte is surrounded by a single layer of flat follicular cells, called a primordial follicle
• ovarian cortex surrounding the primordial follicles consists of collagen fibers and fibroblast-like stromal cells
• at birth, about 2000000 primary oocytes remain
• 40000 are still present at puberty and around 400 will mature and ovulate during woman’s reproductive lifetime
• remainder of primary oocytes undergo atresia

Question 24

Graafian Follicle

Answer 24

• secondary follicle becomes mature follicle; before ovulation, diploid primary oocyte completes meiosis 1 producing two haploid
• smaller cell is first polar body; larger is secondary oocyte
• meosis 2 begins but stops in metaphase
• ovulation: mature follicle ruptures
• secondary oocyte splits into two haploid cells; larger is ovum smaller is second polar body
• nuclei of sperm cell and ovum then unite forming zygote

Question 25

Uterine Tubes

Answer 25

• fallopian tubes or oviducts extend laterally from uterus
• tranpost secondary oocytes and fertalized ova from ovaries to uterus
• infundibulum is close to ovary but is open to peritoneal cavity
• infundibulum extends medially and eventually inferiorly and attaches to superior lateral angle of uterus
• ampulla of uterine tube is widest, longest portion, making up lateral two-thirds of its length
• isthmus of uterine tube is more medial, short, narrow, thick wall portion that joins the uterus
• uterine tubes are composed of 3 layers: mucosa, muscularis, and serosa

Question 26

Uterus

Answer 26

• womb serves as part of pathway for sperm and is site of implantation of fertalized ovum, development of fetus during pregnancy and labor
• uterus is largers in pregnant females and atrphied when sex hormone levels are low
• anatomical subdivisions include the fundus, body and cerviz that opens into vagina
• interior body of uterus is called uterine cavity and interior of narrow cervix is called cervical canal
• cervical canal opens into uterine cavity at the internal os and into the vagina at the external os

Question 27

Ligaments

Answer 27

• broad ligaments: uterus to either side of pelvic cavity
• uterosacral ligaments: connect uterus to sacrum
  cardinal (lateral cervical) ligaments: extend from pelvic wall to cervix and vagina
• round ligaments: extend from a point on the uterus just inferior to uterine tubes to a portion of the labia majora of external genitalia

Question 28

Histology of Uterus

Answer 28

• consists of 3 layers of tissue: perimetrium, myometrium, endometrium
• outer layer: anteriorly forms shallow pouch, vesticouterine pouch; posteriorly forms a deep pouch the rectouterine pouch
• middle layer consists of 3 layers of smooth muscle fibers that are thickest in fundus and thinnest in cervix
• inner layer is highly vascularized and composed of 3 components: simple columnar, lamina propria and endometrial glands
• stratum functionalis lines that uterine cavity and sloughs off during menstruation and deepest layer, stratum basalis is permanent and gives rise to new stratum functionalis

Question 29

Vagina

Answer 29

• lined with mucous membrane
• receptacle for penis during sexual intercourse, outlet for menstrual flow and passageway for childbirth
• nonkertinized stratified squamous and lamina propria that lies in the rugae
• dendritic cells in mucusa are antigen-presenting cells
• mucosa of vagina contains large stores of glycogen, decomposition of which produces organic acids
• resulting acidic environment retard microbial growth, but it is also harmful to sperm

Question 30

Vulva

Answer 30

• anterior to vaginal and urethral opening is mons pubis, elevation of adipose tissue covered by skin and coarse pubic hair that cushions that pubic symphysis
• 2 longitudinal folds of skin, labia majora is covered by pubic hair and contain abundance of adipose tissue, sebaceous glands, and aprocrine sudoriferous glands
• labia majora is homologous to scrotum in males
• medial to labia majora are 2 smaller folds of skin called labia minora and devoid of pubic hair and fat and have few sudoriferous glands but they contain many sebaceous glands
• labia minora are homolgous to spongy urethra

Question 31

Clitoris

Answer 31

• mass of erectile tissue and nerves located at anterior junction of labia minora
• layer of skin called prepuce of clitoris is formde at point where labia minora unite and covers body of the clitoris
• body has two bodies of erectile tissue, corpora cavernosa and glans clitoris
• glans clitoris is homologous to glans penis in males

Question 32

Mammary Glands

Answer 32

• anterior to pectoralis major and serratus anterior muscles and attached by fascia composed of dense irregular tissue
• nipple is a series of closely spaced openings of ducts called lactiferous ducts where milk emerges
• alveoli within lobules produces milk which is stored in lactiferous sinus and then carried out via lactiferous ducts to the surface of the breast
• areola contains modified sebaceous glands
• strands of connective tissue called suspensory ligaments of the breat (Cooper’s Ligaments) run between the skin and fascia and support the breast

Question 33

Muscles of Pelvic Floor

Answer 33

• levator ani and ischiococcygenous muscles, along the fascia which covers them, form the pelvic diaphragm
• pelvic diaphragm separates pelvic cavity above from the perineum below
• perineum is diamond shaped area inferior to the pelvic diaphragm that extends from pubic symphysis anteriorly, to the coccyx posteriorly, and to the ischial tuberosities laterally
• perineal muscles are arranged in two layers; superficial and deep
• deep muscles of perineum assist in urination and ejaculation in males and urination and compression of vagina in females