A&P II exam 5

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1

The Lymphatic System & Lymphoid Organs and Tissues

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Two parts

  • Lymphatic system
  • Lymphoid tissues and organs

Lymphatic system functions

  • Transport fluids back to the blood
  • Absorb digested fat at the intestinal villi
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Lymphoid Organs and Tissues

Play essential roles in body defense and resistance to disease

  • House phagocytic cells and lymphocytes
  • Structural basis for immune system
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Figure 19.2 The relationship of blood vessels to each other and to lymphatic vessels

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Lymphatic System

  • Fluid remaining in tissue spaces = Interstitial fluid

–Escaped from bloodstream

–Needs to get back

–Lymphatic system

  • Collects interstitial fluid and delivers to bloodstream
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Lymphatic Characteristics

lymph – excess fluid carried by lymphatic vessels (enters at lymphatic capillaries – porous)

Properties of lymphatic vessels

  • One way system toward the heart
  • No pump
  • Lymph moves toward the heart
  • Milking action of skeletal muscle
  • Rhythmic contraction of smooth muscle in vessel walls
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Lymphatic Vessels and Capillaries

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Lymphatic Vessels

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Lymphatic collecting vessels

  • Collects lymph from lymph capillaries
  • Carries lymph to and away from lymph nodes
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Lymphatic Vessels

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Lymphatic collecting vessels (continued)

  • Returns fluid to circulatory veins near the heart
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Structures Involved in Absorption of Nutrients

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  • Lacteals (specialized lymphatic capillaries)
  • Absorb dietary fats
  • In small intestine
  • Allows fats to enter bloodstream another way (too large to directly enter blood capillaries)
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Lymph

Materials returned to the blood

  • Water
  • blood cells
  • Proteins
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Lymph

harmful materials that enter lymph vessels

  • Bacteria
  • Viruses
  • Cancer cells
  • Cell debris
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Lymph Nodes

  • filter & cleanse lymph before it is returned to the blood (and activates defenses)
  • Associated with immune System
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Lymph Nodes

defense cells within lymph nodes

  • macrohphages– engulf and destroy foreign substances
  • Lymphocytes – provide immune response to antigens (non-self particles; bacteria, viruses, cancer cells)
  • Arise in red bone marrow
  • T cells: manage immune response; attack foreign cells
  • B cells: produce plasma cells, which secrete antibodies --> Antibodies immobilize antigens
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Lymph Nodes

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Lymph Node Structure

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Other Lymphoid Organs

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Several other organs contribute to lymphatic function and body protection

  • Spleen
  • Thymus
  • Tonsils
  • Peyer’s patches

Only lymph nodes filter lymph

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The Spleen

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Located on the left side of the abdomen

  • lymphocyte proliferation; immune surveillance & response
  • Filters blood
  • Destroys worn out blood cells & platelets from blood
  • Its macrophages remove debris & foreign matter from blood

Forms blood cells in the fetus

Acts as a blood reservoir

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The Thymus

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Located low in the throat, overlying the heart

Functions at peak levels only during childhood

  • Function decreases with time

Doesn’t directly fight antigens

Maturation site for lymphocyte precursors

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Mucosa-Associated Lymphatic Tissue (MALT)

Lymphoid tissues located in mucous membranes throughout body

  • Protects us from pathogens trying to enter body

Includes:

  • Tonsils
  • Peyer’s patches
  • Appendix
  • Other small accumulations of lymphoid tissue

Acts as a guard to protect respiratory and digestive tracts

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Tonsils

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  • Small masses of lymphoid tissue (lymphocytes) around the pharynx
  • Trap and remove bacteria and other foreign materials that enter pharynx via food or air
  • Tonsillitis is caused by bacterial infection
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Peyer’s Patches

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  • Found in the wall of the small intestine
  • Large clusters of lymphoid tissue
  • Capture and destroy bacteria in the intestine
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Appendix

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  • Tubular offshoot of large intestine
  • High concentration of lymphatic tissue

–Destroy bacteria of intestines

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Immunity

  • Immun” = free
  • Resistance to disease
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Body Defenses

Body is constantly in contact with bacteria, fungi, and viruses (pathogens)

Two defense systems for foreign materials

1. nonspecific (innate) defense system

  • Mechanisms protect against a variety of pathogens (harmful or disease causing microorganisms)
  • Responds immediately to protect body from foreign materials
  • First & second lines of defense
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Body Defenses

2. specific (adaptive) defense system

  • Specific defense is required for each type of invader
  • Also known as the immune system
  • Third line of defense
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Body Defenses

  • Nonspecific and Specific systems work hand in hand

–Release and recognize many of the same molecules

–proteins in nonspecific system alert the specific system of foreign molecules

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Nonspecific Body Defenses

Body surface coverings

  • Intact skin
  • Mucous membranes

Specialized cells to inhibit spread of invaders

Chemicals produced by the body

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Surface Membrane Barriers –
First Line of Defense

The skin

  • physical barrier to foreign materials
  • pH of the skin is acidic to inhibit bacterial growth
  • Sebum is toxic to bacteria
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Surface Membrane Barriers –
First Line of Defense

Mucous Membranes

  • stomach mucosa
  • Secretes hydrochloric acid (inhibits bacterial growth)
  • Has protein-digesting enzymes (kill bacteria)
  • saliva and lacrimal fluid contain lysozyme (bacteria destroying enzyme)
  • Mucus traps microogranisms in digestive and respiratory pathways
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Defensive Cells

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phagocytes
(neutrophils and macrophages)

  • Engulfs foreign material into a vacuole
  • Enzymes from lysosomes digest the material
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Defensive Cells

Natural killer cells

  • Can lyse and kill cancer cells
  • Can destroy virus- infected cells
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Inflammatory Response -
Second Line of Defense

Triggered when body tissues are injured

Produces four cardinal signs

  • Redness
  • heat
  • Swelling
  • pain

Results in a chain of events leading to protection and healing

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Functions of the Inflammatory Response

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  • Prevents spread of damaging agents
  • Disposes of cell debris and pathogens
  • Sets the stage for repair
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Antimicrobial Proteins

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Attack microorganisms directly

Complement

  • A group of at least 20 plasma proteins
  • Activated when they encounter and attach to cells (complement fixation)
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Antimicrobial Proteins

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Complement (continued)

  • Damage foreign cell surfaces
  • Will rupture or lyse the foreign cell membrane
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Action of the complement system against a bacterium

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Fever

Abnormally high body temperature

  • Inhibit the release of iron and zinc from liver and spleen needed by bacteria

Fever also increases the speed of tissue repair

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Specific Defense: The Immune System – Third Line of Defense

  • Antigen specific – recognizes and acts against particular foreign substances
  • Systemic – not restricted to the initial infection site
  • Has memory – recognizes and mounts a stronger attack on previously encountered pathogens
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The Reproductive System

Becomes active at puberty

Gonads (“seeds”) – primary ___ organs

  • testes in males
  • ovaries in females

Gonads produce gametes (“spouses”-sex cells) and secrete sex hormones

  • Sperm – male gametes
  • Ova (eggs) – female gametes
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The Reproductive System

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Male: Produce sperm

Female: Produce eggs and

nurture embryo

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The Reproductive System

Ultimate goal: Produce offspring

Timed out intercourse

  • Sperm fertilizes an egg --> zygote
  • First cell of new individual
  • All body cells arise out of that one cell as development proceeds
  • uterus provides environment for developing embryo (fertilization – week 9) & fetus (week 9 – birth, ~37-41 weeks)
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Male Reproductive System

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Testes – pair of male gonads; produce sperm; surrounded by scrotum (“pouch”)

Duct system – what sperm travel through to arrive outside of body

  • Epididymis
  • Ductus (vas) deferens
  • Ejaculatory duct
  • urethra
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Male Reproductive System

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Accessory organs: seminal vesicle, Prostate gland, bulbourethral gland

  • Empty secretions into ducts during ejaculation

external genitalia: Penis, Scrotum

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Testes

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seminiferous tubules

  • Tightly coiled structures
  • Function as sperm_-forming factories
  • Empty sperm into the rete testis

Sperm travels through the rete testis to the epididymis

Interstitial cells produce androgens such as testosterone

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Epididymis

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  • Comma-shaped, tightly coiled tube (“beside the testes”)
  • Functions to mature and store sperm cells (at least 20 days)
  • Expels sperm with the contraction of muscles in the epididymis walls to the vas deferens
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Ductus Deferens (Vas Deferens)

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  • “Carrying away”
  • Carries sperm from the epididymis to the ejaculatory duct
  • Moves sperm by peristalsis
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Ductus Deferens (Vas Deferens)

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  • Ends in the ejaculatory duct which unites with the urethra
  • Vasectomy – cutting of the (vas) ductus deferens to prevent transportation of sperm (but sperm are still produced)
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Urethra

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  • Extends from the base of the urinary bladder to the tip of the penis
  • Carries both urine and sperm
  • Sperm enters from the ejaculatory duct
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Urethra

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Regions of the urethra

  • Prostatic urethra –surrounded by prostate
  • membranous urethra – from prostatic urethra to penis

Spongy (penile) urethra – runs the length of the penis

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Seminal Vesicles

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Located at the base of the bladder

Produces a thick, yellowish secretion (60% of semen)

  • Fructose (sugar), Vitamin C, Prostaglandins (lipids), Other substances that nourish and activate sperm
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Prostate Gland

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Encircles the upper part of the urethra

Secretes a milky fluid

  • Helps to activate sperm
  • Enters the urethra through several small ducts
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Bulbourethral Glands

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Pea-sized gland inferior to the prostate

Produces a thick, clear mucus

  • Cleanses the urethra of acidic urine
  • Serves as a lubricant during sexual intercourse
  • Secreted into the penile urethra
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Semen

Mixture of sperm and accessory gland secretions

Advantages of accessory gland secretions

  • Fructose provides energy for sperm cells
  • Alkalinity of semen helps neutralize the acidic environment of vagina
  • Semen inhibits bacterialmultiplication
  • Elements of semen enhance sperm motility
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External Genitalia

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Scrotum

  • Divided sac of skin outside the abdomen
  • Maintains testes at 3°C lower than normal body temperature to protect sperm viability
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External Genitalia

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Penis

  • Delivers sperm into the female reproductive tract

Regions of the penis

  • Shaft
  • Glans penis (enlarged tip)
  • Prepuce (foreskin)
  • Folded cuff of skin around distal end
  • Often removed by circumcision
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Spermatogenesis

  • Production of sperm cells
  • Begins at puberty and continues throughout life
  • Occurs in the seminiferous tubules
  • Takes 64 to 72 days
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Anatomy of a Mature Sperm Cell

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  • The only human flagellated cell
  • DNA is found in the head
  • Haploid number of chromosomes (undergoes meiosis in testes)
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Testosterone Production

  • The most important hormone of the testes
  • Produced in interstitial cells
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Testosterone Production

Functions of testosterone

  • Stimulates reproductive organ development
  • Underlies sex drive
  • Causes secondary sex characteristics
  • Deepening of voice
  • Increased hair growth
  • Enlargement of skeletal muscles
  • Thickening of bones
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The Reproductive System

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Male: Gonads = testes; Gametes = sperm

Female: Gonads = ovaries; Gametes = ova (eggs)

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Female Reproductive System

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Ovaries

  • Paired reproductive organ; produces female gametes (ova) and sex hormones (progesterone & estrogen)

Duct System

  • Uterine tubes (fallopian tubes)
  • Uterus
  • Vagina

External genitalia – labial folds

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Female Reproductive System

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Ovaries

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  • Composed of ovarian follicles (sac-like structures)
  • Oocyte (immature egg); Follicular cells
  • Ovulation occurs once per month in adult females

A maturing follicle ruptures & releases its oocyte from the ovary

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Oogenesis

Production of female gametes (oocytes, ova, or eggs)

The total supply of eggs are present at birth

  • Primary oocytes are inactive until puberty (then ovulation begins)
  • Ovaries contain 400,000 oocytes; release about 500 in a lifetime

Oocytes are matured in developing ovarian follicles; takes years to complete

  • Triggered by Follicle stimulating hormone (FSH) (from anterior pituitary)

Reproductive ability ends at menopause

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Ovarian Follicle Stages

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Primary follicle – contains an immature oocyte

Graafian (vesicular) follicle – growing follicle with a maturing oocyte

Ovulation – when the egg is mature the follicle ruptures

  • Occurs about every 28 days
  • Transforms into a corpus luteum – glandular structure (eventually degenerates)
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Ovarian cycle:

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Ovarian cycle: Structural changes in the ovarian follicles during the
ovarian cycle are correlated with changes in the endometrium of the
uterus during the uterine cycle.

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Uterine (Fallopian) Tubes

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  • Attaches to the uterus
  • Does not physically attach to the ovary
  • Receive the ovulated oocyte (size of a grain of sand)
  • Provide a site for fertilization
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Uterine (Fallopian) Tube Function

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  • Fimbriae – finger-like projections at the distal end that receive the oocyte
  • Cilia inside the uterine tube slowly move the oocyte towards the uterus (takes 3–4 days)
  • fertilization occurs inside the uterine (fallopian) tube (must happen within 24 hours of ovulation)
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Uterus

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  • Located between the urinary bladder and rectum
  • Hollow organ

Functions

  • Receives, retains and nourishes the fertilized egg
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Regions of the Uterus

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  • Fundus – area where uterine (fallopian) tube enters
  • Body – main portion
  • Cervix – narrow outlet that protrudes into the vagina
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Walls of the Uterus

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Endometrium

  • inner layer; Allows for implantation of a fertilized egg; sloughs off if no pregnancy occurs (menses)

Myometrium – middle layer of smooth muscle

Perimetrium– outermost serous layer

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Menstrual (Uterine) Cycle

Cyclic changes of the endometrium

Regulated by cyclic production of estrogens and progesterone (in ovaries)

  • Coordinated with ovariancycle
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Stages of the Menstrual (Uterine) Cycle

Menses – functional layer of the endometrium is sloughed (days 1-5)

proliferative stage – regeneration of functional layer (days 6-14)

  • Cervical mucus thins; facilitate sperm entry into the uterus.
  • Ovulation occurs in the ovary at the end of the proliferative stage, around day 14.

Secretory stage – endometrium increases in size and readies for implantation (Days 15-28)

  • Cervical mucus becomes thick and sticky, forming a cervical plug that blocks entry of sperm or pathogens
  • Fertilization: fertilized egg implants in uterus; No fertilization: endometrium sloughed, cycle restarts
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Coordination of the Ovarian and Uterine Cycles

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Vagina

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Location

  • Extends from cervix to exterior of body
  • Behind bladder and in front of rectum

Function

  • Serves as the birth canal
  • Passageway for menstrual blood
  • Receives the penis and semen during sexual intercourse
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Hormone Production by the Ovaries

Estrogens

  • Produced by follicle cells in ovaries
  • Cause secondary sex characteristics
  • Development of breasts
  • Appearance of pubic hair
  • Increase in fat beneath the skin
  • Widening and lightening of the pelvis
  • Adaptations for childbirth
  • Onset of menses
77

Hormone Production by the Ovaries

Progesterone

  • Produced by the corpus luteum
  • Development of breasts
  • Enhances beating of cilia in uterine tube
  • Promotes meeting of sperm and oocyte
  • Helps maintain pregnancy
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Stages of Pregnancy and Development

  • Fertilization:sperm+egg-->zygote
  • Embryonic development: start of cell division – 9th week
  • Fetal development: 9 weeks – full term (37-41 weeks)
  • Childbirth
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Early Embryonic Stages:
From Ovulation to Implantation

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Fertilization

Oocyte (egg)

  • Viable for 12 to 24 hours after ovulation

Sperm

  • Viable for 12 to 48 hours after ejaculation

Fertilization is only possible if sperm make it to the fallopian tube

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Mechanisms of Fertilization

Membrane receptors on an oocyte

  • Makes contact with first sperm cell to arrive
  • Does not permit a second sperm head to enter

Fertilization occurs when

  • Genetic material of a sperm combines with that of an oocyte to form a zygote
  • Sperm + oocyte = zygote
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The Zygote

  • First cell of a new individual
  • Fusion of DNA from sperm and egg
  • Begins rapid mitotic cell divisions
  • Zygote stage is in the uterine tube, moving toward the uterus
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The Embryo

  • Developmental stage from the start of cleavage (cell division) until the ninth week
  • First undergoes division without growth
  • Enters the uterus at the 16-cell state
  • Floats free in the uterus temporarily
  • Uterine secretions are used for nourishment
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The Blastocyst

Ball-like circle of cells

Begins at about the 100 cell stage

Primary germ layers are eventually formed

  • Ectoderm – outside layer
  • Mesoderm – middle layer
  • endoderm – inside layer

Late blastocyst implants in the wall of the uterus (day 7)

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Derivatives of Germ Layers

Ectoderm

  • nervous system
  • Epidermis of the skin

mesoderm

  • Everything else

Endoderm

  • Mucosae
  • Glands
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Hormonal Birth Control

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Birth control method that releases hormones

  • Prevents the release of a mature egg (no ovolation)
  • Thickens cervical mucous
  • Changes the lining of the uterus
  • Typical effectiveness rate is 92-99.7%
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Intrauterine Device - IUD

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A T-shaped device inserted into the uterus

Contains the hormone levonorgestrel ( a progestin)

Inserted into the uterus by physician -Prevents the _______ of a mature egg

  • No ovulation

-Thickens ________ mucous

-Changes the lining of the uterus

-Typical effectiveness rate is 98%

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Non-hormonal birth control:
Male Condoms

  • Thin latex or polyurethane that fits over an erect penis
  • Catches sperm during ejaculation to prevent it from entering the vaginal/cervical canal
  • Typical effectiveness is 85-98%
89

Intrauterine Device - IUD

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A T-shaped device with a copper wire

Contains no hormones

Inserted into the uterus by physician

-Prevents sperm from fertilizing the egg

  • Disrupting sperm mobility and damaging sperm
  • Copper acts as spermicide

-Decreases the ability of the sperm to penetrate the cervical mucus

-Changes the lining of the uterus

-Typical effectiveness rate is 92-99%

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Female Sterilization: Tubal ligation

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Surgical procedure

-Close or block the fallopian tubes

  • Ensures sperm and egg do not meet
  • Permanent
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Male Sterilization: Vasectomy

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Surgical procedure

  • Close or block the vas deferens
  • Permanent