PowerPoint Lecture Slides prepared by Jason LaPres Lone Star College North Harris Structures of the Reproductive System Gonads organs that produce gametes and hormones Ducts receive and transport gametes ID: 779392
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Slide1
Slide2C h a p t e r
26
The Reproductive System
PowerPoint® Lecture Slides prepared by Jason LaPres
Lone Star College - North Harris
Slide3Structures of the Reproductive System
Gonads
: organs that produce gametes and hormonesDucts: receive and transport gametesAccessory glands: secrete fluids into ductsPerineal structures: collectively known as
external genitalia
Slide4Structures of the Reproductive System
The Reproductive Tract
Includes all chambers and passageways that connect ducts to the exterior of the body
Slide5Structures of the Reproductive System
Male and Female Reproductive Systems
Are functionally differentFemale produces one gamete per monthRetains and nurtures zygoteMale disseminates large quantities of gametes
Produces 1/2 billion sperm per day
Slide6Structures of the Reproductive System
The Male Reproductive System
Testes or male gonadsSecrete male sex hormones (androgens)Produce male gametes (spermatozoa or sperm)
Slide7Structures of the Reproductive System
The Female Reproductive System
Ovaries or female gonadsRelease one immature gamete (
oocyte) per monthProduce hormones
Uterine tubes
Carry oocytes to uterus:
if sperm reaches oocyte, fertilization is initiated and oocyte matures into
ovum
Uterus
Encloses and supports developing embryo
Vagina
Connects uterus with exterior
Slide8Male Reproductive Functions
Pathway of
Spermatozoa TestisEpididymisDuctus deferens (vas deferens)
Ejaculatory ductUrethra
Slide9Male Reproductive Functions
Accessory Organs
Secrete fluids into ejaculatory ducts and urethraSeminal glands (vesicles)Prostate glandBulbo-urethral glands
Slide10Male Reproductive Functions
External Genitalia
Scrotum Encloses testesPenisErectile organContains distal portion of urethra
Slide11Male Reproductive Functions
Figure 26–1 The Male Reproductive System.
Slide12Male Reproductive Functions
The Testes
Egg shaped5 cm long, 3 cm wide, 2.5 cm thick (2 in. x 1.2 in. x 1 in.)Weighs 10–15 g (0.35-0.53 oz)Hangs in scrotum
Slide13Male Reproductive Functions
The Scrotum
Is a fleshy pouch Suspended inferior to perineumAnterior to anusPosterior to base of penis
Slide14Male Reproductive Functions
Descent of the Testes
Testes form inside body cavityAre adjacent to kidneys
Gubernaculum testisIs a bundle of connective tissue fibers
Extends from testis to pockets of peritoneum
Locks testes in position (near anterior abdominal wall) as fetus grows
Slide15Male Reproductive Functions
Descent of the Testes
During seventh monthFetus grows rapidlyCirculating hormonesStimulate contraction of gubernaculum testis
Each testisMoves through abdominal musculatureIs accompanied by pockets of peritoneal cavity
Slide16Male Reproductive Functions
Figure 26–2a The Descent of the Testes.
Slide17Male Reproductive Functions
Figure 26–2b The Descent of the Testes.
Slide18Male Reproductive Functions
Figure 26–2b The Descent of the Testes.
Slide19Male Reproductive Functions
Accessory Structures
Accompany testis during descentForm body of spermatic cordDuctus deferens
Testicular blood vessels, nerves, and lymphatic vessels
Slide20Male Reproductive Functions
The Spermatic Cords
Extend between abdominopelvic cavity and testesConsist of layers of fascia and muscleEnclose ductus deferens, blood vessels, nerves, and lymphatic vessels of testes
Pass through inguinal canal
Are passageways through abdominal musculature
Form during development as testes descend into scrotum
Descend into scrotum
Slide21Male Reproductive Functions
Blood Vessels of Testes
Deferential arteryTesticular arteryPampiniform plexus
of testicular veinNerves of TestesBranches of genitofemoral nerve
From lumbar plexus
Slide22Male Reproductive Functions
Male Inguinal Hernias
Are protrusions of visceral tissues into inguinal canalSpermatic cord (in closed inguinal canal)Causes weak point in abdominal wall
Female Inguinal CanalsAre very smallContain ilioinguinal nerves and round ligaments of uterus
Slide23Male Reproductive Functions
Figure 26–3 The Male Reproductive System in Anterior View.
Slide24Male Reproductive Functions
The Scrotum and the Position of the Testes
Is divided into two chambers, or scrotal cavitiesEach testis lies in a separate scrotal chamberRaphe
Is a raised thickening in scrotal surfaceMarks partition of two scrotal chambers
Slide25Male Reproductive Functions
Tunica Vaginalis
Is a serous membraneLines scrotal cavityReduces friction between opposing surfacesParietal (scrotal)
Visceral (testicular)
Slide26Male Reproductive Functions
The
Dartos Muscle Is a layer of smooth muscle in dermis of scrotumCauses characteristic wrinkling of scrotal surface
The Cremaster MuscleIs a layer of skeletal muscle deep to dermis
Tenses scrotum and pulls testes closer to body (temperature regulation)
Slide27Male Reproductive Functions
Temperature Regulation
Normal sperm development in testesRequires temperatures 1.1°C (2°F) lower than body temperature Muscles relax or contractTo move testes away or toward body
To maintain acceptable testicular temperatures
Slide28Male Reproductive Functions
Structure of the Testes
Tunica AlbugineaIs deep to tunica vaginalis
A dense layer of connective tissue rich in collagen fibersContinuous with fibers surrounding epididymis
Fibers extend into substance of testis and form fibrous partitions, or
septa
, that converge near entrance to epididymis
Supports blood and lymphatic vessels of testis and
efferent ductules
Slide29Male Reproductive Functions
Histology of the Testes
Septa subdivide testis into lobulesLobules contain about 800 slender and tightly coiled
seminiferous tubules Produce spermEach is about 80 cm (32 in.) long
Testis contains about 1/2 mile of tightly coiled seminiferous tubules:
Form a loop connected to
rete testis
, a network of passageways
Slide30Male Reproductive Functions
Efferent Ductules
15–20 large efferent ductulesConnect rete testis to epididymis
Slide31Male Reproductive Functions
Figure 26–4 The Structure of the Testes.
Slide32Male Reproductive Functions
Connective Tissue Capsules
Surround tubulesAreolar tissue fills spaces between tubulesWithin those spaces, there are
Blood vesselsLarge interstitial cells
(cells of Leydig):
produce androgens: dominant male sex hormones
testosterone is the most important androgen
Slide33Male Reproductive Functions
Spermatogenesis
Is the process of sperm productionBegins at outermost cell layer in seminiferous tubulesProceeds toward lumen
Slide34Male Reproductive Functions
Five Cells of Spermatogenesis
Spermatogonia (stem cells) divide by mitosis to produce two daughter cells:
One remains as spermatogoniumSecond differentiates into primary spermatocyte
Primary spermatocytes
begin meiosis and form secondary spermatocytes
Secondary spermatocytes
differentiate into
spermatids
(immature gametes)
Slide35Male Reproductive Functions
Five Cells of Spermatogenesis
Spermatids:Differentiate into spermatozoa
Spermatozoa:Lose contact with wall of seminiferous tubule
Enter fluid in lumen
Slide36Male Reproductive Functions
Figure 26–5a The Seminiferous Tubules.
Slide37Male Reproductive Functions
Figure 26–5b The Seminiferous Tubules.
Slide38Male Reproductive Functions
Figure 26–5c The Seminiferous Tubules: Stages in Spermatogenesis.
Slide39Male Reproductive Functions
Figure 26–5d The Seminiferous Tubules: Stages in Spermatogenesis.
Slide40Male Reproductive Functions
Contents of Seminiferous Tubules
SpermatogoniaSpermatocytes at various stages of meiosisSpermatids
SpermatozoaLarge nurse cells
(also called sustentacular cells or Sertoli cells)
Are attached to tubular capsule
Extend to lumen between other types of cells
Slide41Male Reproductive Functions
Spermatogenesis
Involves three integrated processesMitosisMeiosisSpermiogenesis
Slide42Male Reproductive Functions
Mitosis
Is part of somatic cell divisionProduces two diploid daughter cellsBoth have identical pairs of chromosomes
Slide43Male Reproductive Functions
Meiosis
Is a special form of cell division involved only in production of gametesSpermatozoa in males
Oocytes in femalesGametes contain 23 chromosomes, half the normal amount
Fusion of male and female gametes produces
zygote
with 46 chromosomes
In seminiferous tubules
Begins with primary spermatocytes
Produces spermatids (undifferentiated male gametes)
Slide44Male Reproductive Functions
Spermiogenesis
Begins with spermatidsSmall, relatively unspecialized cellsInvolves major structural changesSpermatids differentiate into mature
spermatozoaHighly specialized cells
Slide45Male Reproductive Functions
Mitosis and Meiosis
Meiosis I and meiosis IIProduce four haploid cells, each with 23 chromosomes
Prophase IChromosomes condense
Each chromosome has two chromatids
Synapsis
:
maternal and paternal chromosomes come together
four matched chromatids form
tetrad
Crossing over: exchange of genetic material that increases genetic variation among offspring
Slide46Male Reproductive Functions
Mitosis and Meiosis
Metaphase ITetrads line up along metaphase plateIndependent assortment:
as each tetrad splitsmaternal and paternal components are randomly distributed
Anaphase I
Maternal and paternal chromosomes separate
Each daughter cell receives whole chromosome:
maternal or paternal
Slide47Male Reproductive Functions
Mitosis and Meiosis
Telophase I endsWith formation of two daughter cellsWith unique combinations of chromosomesBoth cells contain 23 chromosomes with two chromatids each (
reductional division)
Slide48Male Reproductive Functions
Mitosis and Meiosis
InterphaseSeparates meiosis I and meiosis IIIs very briefDNA is not replicated
Slide49Male Reproductive Functions
Mitosis and Meiosis
Meiosis IIProceeds through prophase II and metaphase IIAnaphase II
Duplicate chromatids separateTelophase II
Yields four cells, each containing 23 chromosomes (
equational division
)
Slide50Male Reproductive Functions
Figure 26–6 Chromosomes in Mitosis and Meiosis.
Slide51Male Reproductive Functions
Figure 26–7 Spermatogenesis.
Slide52Male Reproductive Functions
Spermiogenesis
Is the last step of spermatogenesisEach spermatid matures into one spermatozoon (sperm)Attached to cytoplasm of nurse cells
Slide53Male Reproductive Functions
Spermiation
At spermiation, a spermatozoonLoses attachment to nurse cellEnters lumen of seminiferous tubuleSpermatogonial division to spermiation
Takes about 9 weeks
Slide54Male Reproductive Functions
Nurse Cells
AffectMitosisMeiosisSpermiogenesis in seminiferous tubules
Slide55Male Reproductive Functions
Six Major Functions of Nurse Cells
Maintain blood–testis barrier
Support mitosis and meiosis
Support spermiogenesis
Secrete inhibin
Secrete androgen—binding protein (ABP)
Secrete Müllerian—inhibiting factor (MIF)
Slide56Male Reproductive Functions
Maintenance of Blood–Testis Barrier
Blood–testis barrier isolates seminiferous tubulesNurse cells are joined by tight junctions that divide seminiferous tubule into compartmentsOuter basal compartment
contains spermatogoniaInner lumenal compartment, or adlumenal compartment, is where meiosis and spermiogenesis occur
Slide57Male Reproductive Functions
Support of Mitosis and Meiosis
Nurse cells are stimulated byFollicle-stimulating hormone (FSH)TestosteroneStimulated nurse cells promote
Division of spermatogoniaMeiotic divisions of spermatocytes
Slide58Male Reproductive Functions
Support of Spermiogenesis
Nurse cellsSurround and enfold spermatidsProvide nutrients and chemical stimuli for developmentPhagocytize cytoplasm shed by developing spermatids
Slide59Male Reproductive Functions
Inhibin
Is a peptide hormone secreted by nurse cells in response to factors released by spermatozoaDepressesPituitary production of FSH
Hypothalamic secretion of GnRHRegulation of FSH and GnRH by Inhibin
Gives nurse cells feedback control of spermatogenesis
After division, increases inhibin production
Slide60Male Reproductive Functions
Androgen-Binding Protein (ABP)
Binds androgens (primarily testosterone)In seminiferous tubule fluidIs important in
Elevating androgen in seminiferous tubulesStimulating spermiogenesis
Production of ABP is stimulated by FSH
Slide61Male Reproductive Functions
Müllerian-Inhibiting Factor (MIF)
Is secreted by nurse cells in developing testesCauses regression of fetal Müllerian (paramesonephric) ducts
Help form uterine tubes and uterus in femalesIn males, inadequate MIF production leads to:retention of ducts
failure of testes to descend into scrotum
Slide62Male Reproductive Functions
Sperm Structure
HeadNeck (attaches head to middle piece)Middle piece Tail
Slide63Male Reproductive Functions
Anatomy of a Spermatozoon
HeadA flattened ellipse that contains nucleus and chromosomes Acrosomal cap
at tip of head: is a membranous compartment that contains enzymes essential to fertilization
made of fused saccules of spermatid’s Golgi apparatus
Slide64Male Reproductive Functions
Anatomy of a Spermatozoon
Middle piece Contains mitochondria:in spiral around microtubulesactivity provides ATP to move tail