A&P II exam 5

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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

Lymphoid Organs and Tissues

Play essential roles in body defense and resistance to disease

  • House phagocytic cells and lymphocytes
  • Structural basis for immune system

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

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

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

Lymphatic Vessels

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Lymphatic collecting vessels (continued)

  • Returns fluid to circulatory veins near the heart

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)


Materials returned to the blood

  • Water
  • blood cells
  • Proteins


harmful materials that enter lymph vessels

  • Bacteria
  • Viruses
  • Cancer cells
  • Cell debris

Lymph Nodes

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

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

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


Mucosa-Associated Lymphatic Tissue (MALT)

Lymphoid tissues located in mucous membranes throughout body

  • Protects us from pathogens trying to enter body


  • 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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  • 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

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

–Destroy bacteria of intestines



  • Immun” = free
  • Resistance to disease

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

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

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


Nonspecific Body Defenses

Body surface coverings

  • Intact skin
  • Mucous membranes

Specialized cells to inhibit spread of invaders

Chemicals produced by the body


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

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

Defensive Cells

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(neutrophils and macrophages)

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

Defensive Cells

Natural killer cells

  • Can lyse and kill cancer cells
  • Can destroy virus- infected cells

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


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

Antimicrobial Proteins

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Attack microorganisms directly


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

Antimicrobial Proteins

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Complement (continued)

  • Damage foreign cell surfaces
  • Will rupture or lyse the foreign cell membrane

Action of the complement system against a bacterium

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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


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

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

The Reproductive System

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Male: Produce sperm

Female: Produce eggs and

nurture embryo


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)

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

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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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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  • 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

Ductus Deferens (Vas Deferens)

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  • “Carrying away”
  • Carries sperm from the epididymis to the ejaculatory duct
  • Moves sperm by peristalsis

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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  • 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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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


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

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

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


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

External Genitalia

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

External Genitalia

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  • 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


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

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)

Testosterone Production

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

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

The Reproductive System

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Male: Gonads = testes; Gametes = sperm

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


Female Reproductive System

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

Duct System

  • Uterine tubes (fallopian tubes)
  • Uterus
  • Vagina

External genitalia – labial folds


Female Reproductive System

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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



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)

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.


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

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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  • Located between the urinary bladder and rectum
  • Hollow organ


  • Receives, retains and nourishes the fertilized egg

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

Walls of the Uterus

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  • 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


Menstrual (Uterine) Cycle

Cyclic changes of the endometrium

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

  • Coordinated with ovariancycle

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

Coordination of the Ovarian and Uterine Cycles

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


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

Hormone Production by the Ovaries


  • 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

Hormone Production by the Ovaries


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

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

Early Embryonic Stages:
From Ovulation to Implantation

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Oocyte (egg)

  • Viable for 12 to 24 hours after ovulation


  • Viable for 12 to 48 hours after ejaculation

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


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

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

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

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)


Derivatives of Germ Layers


  • nervous system
  • Epidermis of the skin


  • Everything else


  • Mucosae
  • Glands

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%

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%


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%

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%


Female Sterilization: Tubal ligation

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Surgical procedure

-Close or block the fallopian tubes

  • Ensures sperm and egg do not meet
  • Permanent

Male Sterilization: Vasectomy

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Surgical procedure

  • Close or block the vas deferens
  • Permanent