EXTRA study stuff

IgG: Main form and Most abundant type of antibody in circulation
- production increases after infection or immunization
  - secreted during secondary response
IgA: secreted in mucosal membranes and breast milk
- activity can prevent infection
- mucosal membranes (respiratory tract, digestive tract, reproductive tract, urinary tract) are in external environment
  - IgA within these regions can neutralize pathogen before it gets into tissues, interstitial fluid, or blood /lymph, preventing infection
- good target for certain types of vaccines
IgE: Responsible for allergic reactions in immediate hypersensitivity reactions (e.g. anaphylactic shock)
IgM: antigen receptor on B cell surface prior to infection / immunization
- secreted during primary response
  - B cell surface receptors
  - First antibody produced in response to infection.
IgD: antigen receptor on B cell surface prior to infection / immunization

Sexual Reproduction

Human Life Cycle

Anisogamy: different-sized gametes
- Female Gametes: These are large, referred to as Ova.
- Male Gametes: These are small, referred to as Spermatozoa.
  - Gamete Formation:
    - games are formed through meiosis within the gonads
    - testes: gonads for males
    - ovaries: gonads of females
    - Gametes contain only one copy of each chromosome
      - gametes are haploid = 1n (n= number of chromosomes)
fertilization: union of two gametes to produces zygote
- The fusion of an ovum and spermatozoon.
- zygote = diploid (2n)
  - contains two copies of each chromosome
new individual progresses from zygote $\rightarrow$ embryo $\rightarrow$ fetus
mitosis: daughter cells identical to parent cells
meiosis: formation of gametes

Sex Chromosomes

autosomal chromosomes: first 22 pairs of chromosomes, other than the sex chromosomes.
Sex chromosomes: The X and Y chromosomes; the unequal pairs of chromosomes involved in sex determination (which depends on the presence or absence of a Y chromosome).
- Females: have two $X$ chromosomes ( $XX$ ).
- Males: have one $X$ and one $Y$ chromosome ( $XY$ ).
  - male can only pass on either an $X$ or a $Y$ chromosome
    - Y chromosome has many testis-specific genes
      - testis-specific genes: genes that are related only to development of the testes
    - sex of child is determined by contributing sperm

Bare Bodies

X chromosome inactivation: In females, ONE of the two $X$ chromosomes is inactivated
- This inactivation produces a visible Barr Body
  - ensures that males and females have the same number X-linked genes
  - serve as an easy way to visually determine the sex of a cell.

Chromosomal Sex and Embryonic Gonads

SRY: a specific gene contained in a Y chromosome that codes for a substance known as Testis Determining Factor (TDF).
- Testis Determining Factor (TDF): converts indifferent gonads into testes
  - In the absence of TDF, indifferent gonads naturally become ovaries.

Regulation of Sexual Development

indifferent gonads in presence of TDF results in formation of testes
- testes will secretes two hormones:
  1. anti-mullerian hormone (AMH)
  2. testosterone
    - anti-mullerian hormone (AMH):
      - degenerates paramesonephric (Mullerian) duct
    - testosterone:
      - turns mesonephric (wolffian) duct into:
        epididymides
        ductus deferentia
        ejaculatory ducts
      - turns other embryonic structures into:
        prostate
        penis
        scrotum
indifferent gonads without presence of TDF results in formation of ovaries
- Ovaries will secrete NO AMH and NO testosterone:
  - NO anti-mullerian hormone (AMH):
    - turns paramesonephric (Mullerian) duct into:
      - uterus
      - uterine tubes
  - NO testosterone:
    - degenerates mesonephric (wolffian) duct
    - turns other embryonic structures into:
      - vagina
      - clitoris
      - labia

Development of External Genitalia

in males and females for the first 6 weeks, they have the same undifferentiated structures:
- testosterone masculinizes these into scrotum, prostate gland, spongy urethra, and penis
- without testosterone, these become the labia and clitoris

Overview of Endocrine Regulation for Males and Females

Generalized Functions of FSH and LH

anterior pituitary gland structure:
- Neurons secrete regulatory hormones into capillary bed called hypophyseal portal system at the base of the hypothalamus
  - then delivered to a secondary capillary bed in anterior pituitary gland

Two important hormones produced in the anterior pituitary glands of both males and females
- Follicle Stimulating Hormone (FSH)
- Luteinizing Hormone (LH)
  - FSH and LH are both TROPIC hormones
    - TROPIC hormones: hormones that target another endocrine gland
  - secretion of FSH and LH is stimulated by hypothalamus secreting gonadotropin-releasing hormone (GnRH)
    - gonadotropin-releasing hormone (GnRH): stimulate release of Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH)
      - tropic hormone because targets another endocrine gland
        target gonads (testes and ovaries)
  - Functions of FSH and LH:
    - Stimulation of spermatogenesis (in males) or oogenesis (in females)
    - Stimulation of gonadal hormone secretion
    - Maintenance of the structures of the gonads

Generalized Regulation of FSH and LH

Regulation of FSH and LH:
- hypothalamus releases Gonadotropin-releasing hormone (GnRH)
  - GnRH stimulates the anterior pituitary gland to secrete both Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH)
    - FSH and LH stimulates the gonads produce gametes (sperm or ova)
      - gonads are the effectors
    - FSH and LH also stimulates the secretions of sex steriods and inhibin
      - inhibin: hormone secreted by the seminiferous tubules of the testes that specifically exerts negative feedback control of FSH secretion from the anterior pituitary.
- sex steroids facilitate a negative feedback loop at two different levels:
  - hypothalamus:
    - increase in sex steroids causes decrease in (down regulates) hypothalamus’ secretion of Gonadotropin-releasing hormone (GnRH)
      - hypothalamus has receptors that detect elevated levels of sex steroids
        leads to decreased secretion of GnRH
        hypothalamus acts as sensor, integrating center, and effector
  - Anterior Pituitary Gland:
    - increase in sex steroids down regulates anterior pituitary’s responsiveness of Gonadotropin-releasing hormone (GnRH)
      - anterior pituitary has receptors that detect elevated levels of sex steroids, decreasing responsiveness to GnRH
        leading to a reduction in FSH and LH secretion
        anterior pituitary acts as sensor, integrating center and effector
- Inhibin facilitate a negative feedback loop on FSH:
  - increase in inhibin down regulates the anterior pituitary’s secretion of FSH, without affecting the secretion of LH
    - anterior pituitary has receptors that detect elevated levels inhibin, decreasing the secretion of FSH

The Male Reproductive System

Organs of the Male Reproductive System

testes: male gonads, location where spermatogenesis takes place
- produces sperm
epididymis: coiled tubule where sperm mature or are reabsorbed if not ejaculated
semen: combination of sperm and seminal fluid
- seminal fluid: collection of fluid from seminal vesicles, prostate gland, and bulbourethral gland
  - seminal fluid is:
    - bicarbonate rich
      - male and female reproductive tracts are acidic, bicarbonate neutralizes acidic environment for sperm
    - fructose rich
      - gives semen fuel/ energy source to travel

Testis Structure and Specialized Cells:

Testes contains seminiferous tubules and interstitial fluid
- Seminiferous tubules contains sertoli cells:
  - Stertoli cells: have Follicle Stimulating Hormone (FSH) receptors that influence spermatogenesis
    - sertoli cells cytoplasm surround developing spermatocytes, forming blood-testes barrier
      - blood-testes barrier: barrier formed by Sertoli cells around the seminiferous tubules, which separates the antigens in the spermatogenic cells from the immune system in the blood.
        protects developing sperm
        molecules must pass from through cytoplasm of of sertoli cells before entering developing sperm cells f
    - stermatogenesis is stimulated to FSH
- Interstitial fluid within the testes (between seminiferous tubules) contain Leydig cells:
  - leydig cells: have Luteinizing Hormone (LH) receptors that secretes testosterone in response to LH

Effects of FSH and LH in Males

Regulation of FSH and LH in males:
- hypothalamus releases Gonadotropin-releasing hormone (GnRH)
  - GnRH stimulates the anterior pituitary gland to secrete both Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH)
    - in the testes, receptors on the leydig cells sense the increase in LH
      - leydig cells secrete testosterone in response
        secretion of testosterone causes:
        effects on CNS
        stimulation of bone and muscle growth
        establishment and maintenance of male secondary sex characteristics
        maintenance of accessory glands and organs
    - in the seminiferous tubules of the testes, receptors on the sertoli cells sense the increase in FSH
      - sertoli cells stimulate spermatogenesis and spermiogenesis in response
      - sertoli cells also secrete inhibin in response
        inhibin: inhibits the anterior pituitary’s secretion of FSH, without affecting the secretion of LH
- Testosterone facilitate a negative feedback loop at two different levels:
  - hypothalamus:
    - increase in testosterone inhibits hypothalamus’ secretion of Gonadotropin-releasing hormone (GnRH)
      - hypothalamus has receptors that detect elevated levels of testosterone
        leads to decreased secretion of GnRH
  - Anterior Pituitary Gland:
    - increase in testosterone inhibits anterior pituitary’s secretion of LH, without affecting the secretion of FSH
      - anterior pituitary has receptors that detect elevated levels of testosterone, inhibiting the further release of luteinizing hormone (LH)
        testosterone level is not efficient enough to suppress FSH - needs inhibin to do this
        leading to a reduction in LH secretion
- Inhibin facilitate a negative feedback loop on FSH:
  - increase in inhibin inhibits the anterior pituitary’s secretion of FSH, without affecting the secretion of LH
    - anterior pituitary has receptors that detect elevated levels inhibin, decreasing the secretion of FSH

Spermatogenesis vs Spermiogenesis

Spermatogenesis: formation of 4 viable sperm
- starts during puberty and lasts entire male life span
- starts with spermatogonium (germ cells)
- Process of Spermatogenesis:
  - spermatogonium:
    - spermatogonium (2n) goes through mitosis, forming duplicate of itself called the primary spermatocyte (2n)
  - primary spermatocyte:
    - primary spermatocyte (2n) then goes through meiosis I, resulting in two secondary spermatocytes (1n)
      - meiosis I is basically mitosis, forming two identical cells
  - secondary spermatocytes:
    - two secondary spermatocytes (1n) then proceed to meiosis II, forms four spermatids (1n)
  - spermatids go through spermiogenesis:
    - four spermatids develop into four spermatozoa ( $1n$ )

Spermiogenesis: development of spermatids into spermatozoa, when spermatids get rid of excess cytoplasm and form the flagellum to become efficient for motility
- occurs in the last stage of spermatogenesis
- requires the sertoli cells
  - sertoli cells assist spermatids get rid of excess cytoplasm and develop flagellum

Fertilization, Pregnancy, and Parturition

Major processes:
- Capacitation
- Fertilization
- Implantation
- Gestation
- Parturition
- Lactation

Capacitation

Over 300 million sperm enter the female at ejaculation, but only about 100 of these live to enter the fallopian tube.
- Sperm must become capacitated to enter the fallopian tube to reach the ovum and for fertilization to occur
  - capacitated: making sperm flagellum hyperactive
    - Changes that occur within spermatozoa in the female reproductive tract that enable them to fertilize ova
      - causes flagellum to swim more forcefully
    - takes at least 7 hours after ejaculation
  - can only be capacitated in right environment:
    - increase pH and increase progesterone causes Hyper-activation of the flagellum (capacitation)
      - Capacitated sperm are guided to the oocyte by chemotaxis and thermotaxis
        chemotaxis: chemical secretions from the ovum that attract capacitated sperm
        thermotaxis: warmer temperatures attract the capacitated sperm

Fertilization

Fertilization usually occurs in the uterine tubes.
Acrosomal enzymes on the sperm digest the zona pellucida on its way into the oocyte.
- zona pellucida: protective molecular layer around the ovum
- Acrosome: membranous cap on the head of a sperm that contains digestive, acrosomal enzymes.
  - During fertilization, an acrosomal reaction releases the acrosomal enzymes to digest the zona pellucida
    - allows sperm to tunnel through the zona pellucida and reach the plasma membrane of the oocyte.
      - prevents multiple sperm from entering

Implantation

when sperm gets to uterus, implantation of blastocyst occurs around 6 days after fertilization
- blastocyst: the form of the embryo that implants in the endometrium of the uterus beginning at about the fifth day following fertilization.

Gestation

gestation: approximately 38 weeks long
blastocyst secretes hCG (human chorionic gonadtoropin) which stimulates corpus luteum to continue to secrete estrogen and progesterone
- Human chorionic gonadtoropin (hCG): activates LH receptors in the corpus luteum of the mother’s ovaries to maintain the corpus luteum for the first 10 weeks of pregnancy.
  - stimulates corpus luteum to continue to secrete estrogen and progesterone
    - prevents menses from occurring since there is NO decrease in estrogen and progesterone
placenta: operational by week 5
- placenta functions:
  - serves as digestive, respiratory and excretory system for fetus
  - secretes estrogen, progesterone and hCG
    - takes over the secretion of estrogen, progesterone and hCG after the corpus luteum has been degraded
  - isolation barier
    - prevents mixing of blood from mom to fetus
    - placenta contains capillary beds that facilitate nutrient and gas exchange between maternal and fetal circulation, but prevents transfer of blood
    - fetal hemoglobin has a substantially higher affinity for oxygen than mother
      - allows for fetus to efficiently absorb oxygen from the maternal blood supply

Parturition

Parturition: The process of giving birth
- requires dilation of cervix and contractions of the uterus
- relaxin: hormone secreted by corpus luteum and placenta to loosen connective tissue between plevic bones
- oxytocin: induces uterine contractions

Lactation

several hormones are associated with mammary development and milk production
- prolactin: induces synthesis of enzymes needed for milk production
- oxytocin: essential for milk letdown, where milk is pushed through the ducts

Two Classes of vitamins:

Fat soluble vitamins: stored in fatty tissues and are not excreted from the body - can overdose on these on Vitamins, since they stay stored in fatty tissues
- Vitamin A: involved in dim light vision
- Vitamin D: needed for calcium absorption
- Vitamin E: strong antioxidant
- Vitamin K: needed to make clotting factors
Water Soluble Vitamins: cannot be stored in the body; if intake excess of these vitamins, its excreted out
- Vitamin B’s:
  - Thiamine (vitamin B₁): needed to convert pyruvate to acetyl CoA
  - Riboflavin (vitamin B₂) and Niacin (vitamin B₃): needed to make coenzymes FAD and NAD
  - Pyridoxine (vitamin B₆): needed for amino acid metabolism
- Vitamin C: antioxidants, inactivates free radicals