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Human Anatomy and Physiology

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Human Anatomy and Physiology Chapter 27 Reproductive System The Reproductive System Functions: Produce sex cells (eggs and sperm) Permit the joining of the sex ... – PowerPoint PPT presentation

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Title: Human Anatomy and Physiology


1
Human Anatomy and Physiology
  • Chapter 27 Reproductive System

2
The Reproductive System
  • Functions
  • Produce sex cells (eggs and sperm)
  • Permit the joining of the sex cells
  • Provide an environment for the development of a
    fertilized egg (only in the female)

3
Male Reproductive System
  • The male gonads (organs that produce sex cells)
    are the testes.
  • The testes are held within the scrotum
  • Optimum sperm production occurs at about 3 C
    cooler than internal body temperature
  • The scrotum helps to regulate the temperature of
    the testes
  • The dartos and cremaster muscles
  • Figures 27.1 and 27.2

4
Male Reproductive System
  • The penis contains erectile tissue Figure 27.4

5
Male Reproductive System
  • Inside the testes there is a series of coiled
    tubes called seminiferous tubules (ST)
  • these are the site of sperm production
  • they have a total length of nearly half a mile!
  • Outside the ST are the interstitial or Leydig
    cells that produce testosterone
  • Figure 27.3

6
Male Reproductive System (cont.)
  • Spermatogenesis
  • about 400 million sperm are produced each day!
  • Inside the ST there are two cell types
  • Spermatogenic cells these will become sperm
  • Sertioli cells (sustentacular cells) help
    nourish the germ cells
  • They also form the blood-testis barrier
  • Figure 27.8

7
Male Reproductive System (cont.)
  • Germ Cells
  • Spermatogonia around the periphery of the ST
  • Divide by mitosis to start the process of sperm
    production
  • One cell ? spermatocyte, One cell ? spermatogonia
  • The spermatocytes then proceed through meiosis to
    produce functional sperm cells
  • Figure 27.8

8
Male Reproductive System (cont.)
  • Mature sperm have three distinct parts
  • head - nucleus and acrosome
  • midpiece - contains mitochondria
  • tail - flagellum for motility
  • Figure 27.9

9
Male Reproductive System (cont.)
  • Sperm produced in the testes mature in the
    epididymis
  • They are also stored here for as long as several
    months
  • the epididymis is connected to the urethra by a
    long tube called the vas deferens (ductus
    deferens)
  • vasectomy - severing of the vas deferens
  • Figure 27.1 and Figure from other text

10
Male Reproductive System (cont.)
  • Before leaving the body, sperm are mixed with a
    fluid
  • seminal fluid sperm semen

11
Male Reproductive System (cont.)
  • Seminal fluid is produced by three glands
  • seminal vesicles (60) mucus, fructose,
    fibrinogen, prostaglandins
  • prostate gland (30) enzymes, clotting factors
  • bulbourethral gland (5) mucus
  • The remaining 5 of semen is composed of sperm
  • Normal sperm count is 75-400 million sperm per ml
    of semen
  • Figure 27.1

12
Male Reproductive System (cont.)
  • Hormonal Regulation in Males
  • Hypothalamus Gonadotropin-releasing hormone
    (GnRH)
  • Stimulates the release of the gonadotropins from
    the anterior pituitary gland
  • Luteinizing Hormone (LH) increases testosterone
    production in the Leydig cells
  • Follicle-Stimulating Hormone (FSH) binds to
    Sertioli cells and stimulates sperm cell
    production
  • Figure 27.10

13
Male Reproductive System (cont.)
  • Puberty onset of sexual maturity
  • Human chorionic gonadotropin is produced by the
    placenta during fetal development
  • This stimulates the release of testosterone for
    initial male sex organ development
  • After birth, very little testosterone is produced
    until puberty

14
Male Reproductive System (cont.)
  • At puberty the hypothalamus increases GnRH
    secretion
  • This in turn increases LH and FSH secretion
    resulting in testosterone production
  • Effects of testosterone
  • Development and enlargement of male reproductive
    system
  • Stimulates hair production on face, legs, chest,
    pubic region (and back, occasionally)

15
Male Reproductive System (cont.)
  • Increases rate of sebaceous gland secretion
  • Can result in acne
  • Increases metabolism, RBC production, and protein
    synthesis
  • Causes rapid bone growth (but also stimulates the
    closure of the epiphyseal growth plate)

16
Female Reproductive System
  • The female gonads are the ovaries
  • the ovaries alternate in producing one egg per
    month
  • The ovaries also produce estrogen and
    progesterone (the female sex hormones)
  • Anatomy - Figures 27.11 and 27.14

17
Female Reproductive System (cont.)
  • Oogenesis
  • There are many follicles within the ovaries
  • each follicle contains an immature egg
  • there are about 2 million follicles at birth
  • 300,000-400,000 at puberty
  • only 400 are ever released as mature eggs
  • the egg is released from the ovaries during
    ovulation
  • The corpus luteum is a hormone-secreting gland in
    the ovary
  • Figures 27.12 and 27.19

18
Female Reproductive System (cont.)
  • Puberty
  • Marked by menarche (the first menstrual period)
  • Reproductive organs and breasts enlarge and
    develop
  • Puberty results from estrogen and progesterone
    production

19
Female Reproductive System (cont.)
  • The Menstrual Cycle
  • Typically the cycle lasts 28 days
  • Includes both the ovarian and uterine cycles

20
Female Reproductive System (cont.)
  • The Ovarian Cycle
  • Days 1-14 are the Follicular Phase
  • Day 14 Ovulation
  • Days 14-28 are the Luteal Phase

21
Female Reproductive System (cont.)
  • The Follicular Phase
  • Early in the cycle GnRH secretion increases
  • Effect?
  • FSH and LH stimulate the development of a
    follicle and
  • The production of estrogen by the ovary

22
Female Reproductive System (cont.)
  • A surge of LH results in ovulation
  • It also leads to the development of the corpus
    luteum
  • The corpus luteum secretes estrogen and
    progesterone
  • If fertilization does not occur, the cells of the
    corpus luteum degenerate
  • Estrogen and progesterone secretion then rapidly
    declines and the cycle starts over
  • Figures 27.21 and 27.22

23
Female Reproductive System (cont.)
  • The Uterine Cycle
  • Days 1-5 Menstrual Phase
  • the endometrium is sloughed off
  • Days 6-14 Proliferative Phase
  • endometrium thickens and prepares for pregnancy
  • Caused by estrogen and progesterone
  • Days 15-28 Secretory Phase
  • endometrium continues to thicken and secretions
    increase
  • Figure 27.22, Figure from other text, and CD

24
Female Reproductive System (cont.)
  • Menopause - period when uterine cycles and
    ovulation cease
  • usually occurs between the ages of 45 and 55

25
Fertilization and Pregnancy
  • Fertilization occurs in the fallopian tubes
  • If the egg is fertilized, human chorionic
    gonadotropin is released
  • This keeps the corpus luteum from degenerating
    and stops the uterine cycle
  • The embryo can become embedded in the uterine
    wall
  • Figures from other text and 28.4

26
Fertilization and Pregnancy
  • Timing of intercourse
  • The egg is only viable for 12-24 hours after
    ovulation
  • Sperm cells can survive for 24-72 hours
  • Therefore intercourse must occur between days
    11-15 in the menstrual cycle
  • Even given the right timing, fertilization is not
    certain
  • Figure 28.2 and other figure

27
Fertilization and Pregnancy
  • Twins
  • Fraternal 2 eggs released and fertilized
  • Identical Twins 1 egg separates to form 2
    babies
  • Figures from other text

28
Methods of Birth Control
  • Table and Figures from other text

29
Methods of Birth Control
  • Discussion

30
Infertility
  • 15 of all couples in the US cannot have children
  • these couples would be considered sterile
  • Another 10 have fewer children than they wish
  • these couples are termed infertile
  • The most frequent causes of infertility in
    females are
  • blocked oviducts
  • endometriosis - presence of uterine tissue
    outside the uterus
  • The most frequent cause of infertility in males
    is
  • low sperm count

31
Alternative Methods of Reproduction
  • Artificial Insemination - sperm are placed in the
    vagina by a physician
  • sperm from donor
  • concentrated sperm from husband with low sperm
    count
  • In Vitro Fertilization - sperm and egg are mixed
    in a test tube
  • fertilized egg is placed in the females uterus

32
Alternative Methods of Reproduction (cont.)
  • Gamete Intrafallopian Transfer - eggs and sperm
    are mixed in a test tube
  • they are immediately injected into the fallopian
    tubes
  • Surrogate Mothers - individuals donate eggs
    and/or sperm
  • the surrogate mother carries the fetus
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