These are comprehensive, organised, and easy-to-read notes that cover a three-unit module consisting of eighteen lectures on reproductive physiology, basic concepts of immunology, as well as inflammation. These are perfect for bioscience and animal/veterinary students as well as prospective student...
Bioveterinary Sciences &
Biological Sciences Notes
Royal Veterinary College, D300
Contents
INTEGRATED PHYSIOLOGY I
Reproductive Physiology .......................................................................................................... 1
Fertilisation ..................................................................................................................................... 1
Male Reproduction ......................................................................................................................... 9
Female Reproduction.................................................................................................................... 19
Pregnancy ..................................................................................................................................... 29
Reproductive Technology ............................................................................................................. 36
Parturition ..................................................................................................................................... 43
Basic Concepts of Immunology ............................................................................................... 52
Introduction to Immunology......................................................................................................... 52
Cells of the Immune System ......................................................................................................... 57
Tissues of the Immune Systems.................................................................................................... 67
Antibody Structure and Function.................................................................................................. 73
Antibody-Mediated Immunity ...................................................................................................... 80
Innate Immunity ........................................................................................................................... 86
T Cell-Mediated Immunity ............................................................................................................ 95
T and B Lymphocyte Development ............................................................................................. 110
Immune Responses to Pathogens............................................................................................... 120
The Major Histocompatibility Complex and Immunogenetics ................................................... 131
Inflammation ....................................................................................................................... 138
Acute Inflammation .................................................................................................................... 138
Chronic Inflammation ................................................................................................................. 146
, 1
Fertilisation
Draw and label a sperm cell and identify its organelles.
Explain how sperm move.
Explain the concept of sperm storage.
Explain methods for avoiding retrograde transport of semen. Outline the
maturational changes sperm must undergo in the female tract before
fertilisation can occur explaining the process of capacitation, hyperactivation
and acrosome reaction. Describe the basic requirements for successful
fertilisation.
Describe critical components on sperm and oocyte which interact during the
process of fertilisation.
Outline the early stages of embryo development.
Erection
Psychogenic stimuli which induce an erection include:
Visual cues
- Mating in others
- Lordosis (lowering of the forelimbs but with the rear limbs extended and hips raised)
Ejaculation
Erection involves the stimulation of the pelvic nerve. This
causes arterial dilation and increased blood flow.
Retraction penis muscle relaxes, which causes the sigmoid
flexure to straighten. The muscles of vas deferens, seminal
vesicles and the prostate all contract, causing the
spermatozoa and the seminal plasma (semen) to be
expelled. Ejaculation can be very forceful in some species,
e.g. horse, and can occur either as a single spurt (e.g. bull
1-3 sec) or for an extended period (e.g. camel 6-20 min).
Copulation in the dog
Male mounts the female for 1-2 mins during the first stage
coitus and then does the turn (2-5 sec) to enter the second
stage coitus for 5-45 mins. This creates a high vaginal
pressure to force the sperm into the uterus. Second stage
coitus can be achieved due to the os penis bone which
keeps the penis sturdy. The bulbus glandis locks the penis
inside the vagina by expanding.
The female tract
In order to fertilise the egg, the sperm must:
- Avoid retrograde transport
- Transverse the cervix
- Travel through the uterus
- Travel through the oviduct
- Attaint capacity to fertilise (capacitation and hyperactivation of motility)
- Locate the oocyte (acrosome reaction)
- Penetrate the oocyte
, 3
Avoiding the retrograde transport
60% of sperm is lost within 12 hours in cow and up to 99% is lost in a human. In order to avoid the loss
of sperm, animals came up with some strategies to minimise the loss:
Pig: intrauterine semen deposition
Horse, dog: semen squirted through the cervix at copulation
Dog: maintaining mating position, high pressure
Horse, pig, rodents: viscous gel fraction of seminal plasma acts to ‘plug’ the tract
Sperm structure
The acrosome is a cap over the top of the
sperm head, which contains an enzyme
that will dissolve the zona pellucida of the
oocyte and allow the sperm cell to enter.
The equatorial segment of the acrosome-
reacted sperm is important in initiating
fusion with the egg plasma membrane
during fertilization.
The mitochondrial helical sheath provides
energy for the sperm to move.
Implications for fertility treatment
The object of assisted reproductive technology is to bring the sperm and the egg close together to
increase the chances of fertilisation and achieve pregnancy. This is achieved through IVF or ICSI. The
sperm selected for the procedure must be chosen carefully since sperm abnormality reflects genetic
problems and there is no natural selection in a fertility treatment since the sperm cells don’t have to
compete with each other.
Sperm transport
The sperm movement happens in two phases:
Rapid transport phase
The sperm reaches the oviduct
within minutes
Unable to fertilise the oocyte
Sustained transport phase
Capacitation
Hyperactivation
Acrosome reaction
Ejaculated sperm cannot fertilise the oocyte, it must first undergo capacitation. Sperm capacitation
refers to the physiological changes spermatozoa must undergo in order to have the ability to
penetrate and fertilize an egg. This is achieved by a progressive destabilisation of the plasma
membrane.
Glycoprotein molecules coating the sperm head are removed
Exposure of zona pellucida to binding proteins
Sperm is able to bind to the oocyte at fertilisation
Increased intracellular Ca2+
Membrane fluidity is increased to aid the breakdown of the acrosome
The uterus aids in the steps of capacitation by secreting sterol-binding albumin, lipoproteins,
and proteolytic and glycosidases (glycosidasic enzymes) such as heparin.
Non-mammalian spermatozoa do not require this capacitation step and are ready to fertilize an oocyte
immediately after release from the male. After this capacitation, the sperm must undergo the final
maturation step, activation, involving the acrosome reaction.
, 6
Sperm motility
The sperm moves through the tract due to:
- Motility of sperm
- Viscous fluid currents caused by uterine cilia
- Uterine contractions
The sperm tail provides:
- Energy production (ATP from mitochondrial sheath)
- Propulsive apparatus (axoneme)
Hyperactivation
Capacitated sperm exhibits
hyperactivated motility – strong, wide
amplitude whiplashing tail beats. There
is an increase in intracellular Ca2+, which
leads to elevated cAMP levels. This
increased force is required to swim
through the viscous environment within
the oviduct. In vitro, hyperactivation
leads to more head movement and less
linearity.
Acrosome reaction
Capacitation exposes the zona pellucida binding proteins on the
sperm plasma membrane (ZP3). Sperm binds to the zona
pellucida via ZP3 and sperm binding required 50 000 ZP3
molecules. The binding initiates sperm acrosome reaction:
Fusion of sperm plasma membrane and outer acrosomal
membrane
The release of enzymes to digest the zona pellucida
Exposure of equatorial segment for oocyte fusion
, 7
Fertilisation
Acrosomal enzymes digest a small hole in the zona pellucida. Penetration of the zona pellucida is a
rapid process – the sperm moves into the perivitelline space between the zona and the oocyte plasma
membrane. Oocyte plasma membrane fuses with the sperm equatorial segment and the sperm is
engulfed. Cortical granules from the oocyte move into the perivitelline space to block the zona and
prevent polyspermy.
, 8
Summary
Erection involves sexual responses and genital reflexes.
During erection, the corpus cavernosa fills with blood (high
volume, high pressure) and the retractor penis muscle relaxes.
Copulation and site of semen deposition vary between
species.
Sperm must travel to the oviduct to fertilise the oocyte.
Sperm is motile.
To fertilise sperm must undergo:
- Capacitation
- Hyperactivation
- Acrosome reaction
Sperm binds the zona pellucida via ZP3 proteins.
Cortical granules released from the oocyte cause a zona block to polyspermy.
, 9
Male Reproduction
Describe the structure of the testis from the gross to the cellular level.
Describe the two major activities of the testis.
Describe the anatomical structure of the male reproductive tract.
Describe the stages of spermatogenesis and indicate on a microscopic section
of the testis where each of these stages takes place.
Describe the components of the Hypothalamus-Pituitary-testis axis.
Describe the role of the epididymis in sperm maturation and acquisition of
motility.
Explain the process of erection in two different types of penis.
List the volume of semen and sites of deposition in the various species.
Explain the function of the accessory secretions.
Why study reproduction
Fertility is decreasing with age. Infertility affects 1 in 6
couples and it is one of the most common reason for men
and women (aged 20-445) to visit GP. There is an equal
split in the cause of infertility between the sexes.
Our environment governs fertility
Naturally occurring chemicals influence fertility:
Hops mimic the female hormone oestrogen in males and females
o Disruption of ovarian cycling in females
o Reduced sperm counts in males
Chemical pollutants also mimic reproductive hormones:
Plastics in food packaging mimic oestrogen
o Oestrogenic compounds in plastics are activated by microwave heating
There is evidence that the effects of pollutants on fertility are epigenetic and can have
multigenerational effects.
Impact on wildlife
Pollution, deforestation and the rising global temperature reduce fertility:
Altered seasonal breeding patterns
Hormone disruption and sex change
o A third of male fish in the UK rivers are ‘feminised’ due to pollution levels
Marine mammals are adversely affected
o Constant exposure to pollutants in the water
o Pollutants are held in large fat stores and are passed on to offspring via milk
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