Animal Physiology Higher Level (HL). Antibody Production and Vaccination Fundamentals of the Immune System ▪ When a pathogen enters the body of any mammal

Animal PhysiologyHigher Level (HL)

Antibody Production and VaccinationFundamentals of the Immune System

▪ When a pathogen enters the body of any mammal the immune system responds.

▪ The immune system cannot recognize which “invader” cause disease

▪ Virus vs. transplanted organ.

▪ Recognition is self vs. non-self

▪ All cells in an organism have the same DNA

▪ All cell membranes have a common set of membrane proteins.

▪ Antigen – any molecule that is non-self

Antibody Production and Vaccination

Steps of Mammalian Immune Response

▪ Leucocytes (white blood cells) – contain many different types of B lymphocytes

▪ Each type of B lymphocyte (or plasma cell) is capable of synthesizing and secreting a specific antibody that binds to a specific antigen.

▪ Why do we get sick? Mammals do not have enough of each type of B cell for the amount of antibody secretion.▪ Leucocytes represent only 1% of all cells in the bloodstream

Antibody Production and VaccinationSteps of Mammalian Immune Response

Macrophage – a large phagocytic cell; the first type of leucocyte to encounter an antigen.

▪ Engulfs antigen when it encounters it

▪ Antigen Presentation – pathogen is partially digested and displayed on the cell membrane of the macrophage

▪ Process of engulfing pathogen by the cell?

▪ Helper T cells can chemically recognize the antigen presented & become activated


▪ Helper T cells chemically communicate with the specific B cell that is able to produce the antibody needed.

Communication Line:

Macrophage Presents Antigen Helper T lymphocytes become activated B lymphocytes become activated


▪ T cells (aka T lymphocyte) activate B cell

▪ B cell starts cloning (cell cloning = mitosis)

▪ 2 types of cells produced:

▪ Plasma cells – secrete antibodies immediately and help fight off the first (primary) infection

▪ Memory cells – long lived cells that remain circulating in the bloodstream waiting for subsequent (or secondary) infection.

Plasma cells secrete antibodies


True Immunity

▪ So why do we get “sick”?

▪ Symptoms depends on the speed of replication of pathogen and the type of tissue that is being attacked.

▪ On a second infection the memory cells that were produced during the primary infection are still in the blood stream

▪ These cells live a long time and are in large numbers

▪ They are capable to respond to an attack quickly, with more antibodies than before!


Antibodies

▪ Antibodies are protein molecules

▪ Produced by plasma cell leucocytes in response to specific pathogen

▪ They all have a similar structure

▪ Y shaped proteins with the same amino acid sequences

• At the end (red) are unique 2 sequences of amino acids

• These are the unique binding site to specific pathogen

• Each side is identical and capable of binding to pathogen


Antibodies

▪ Antibodies help the immune system:

1. Binding to the pathogen and marking it for destruction by other cells of the immune system

2. The two binding sites allow the antigens to bind together. This leads to clumps of the pathogens.

▪ This helps macrophages and other phagocytic cells to find the pathogens

3. They also help recruit other cells and proteins to fight pathogens


Vaccines

▪ An organism cannot be immune to a pathogen before being exposed to it at least once.

▪ Vaccines act as the first exposure to a pathogen

▪ A vaccine is composed of chemical components of a pathogen after eliminating the disease causing abilities of the pathogen

▪ Leucocytes responsible for the primary immune response still recognize the chemical as not-self▪ Primary response takes place

▪ This includes the formation of memory B cells capable of producing antibodies very quickly if there is a real pathogen


▪ Vaccination does not prevent an infection

▪ Vaccines contain antigens that trigger immunity but do not cause the disease

▪ The secondary immune response is quicker and results in higher antibody production compared with the primary immune response


Diseases that cross form one species to another (Zoonosis)

▪ HIV/AIDS

▪ Ebola: Symptoms – nausea and vomiting, diarrhea (may be bloody), red eyes, raised rash, Chest pain and cough, Stomach pain, severe weight loss, bleeding, usually from the eyes, and bruising (people near death may bleed from other orifices, such as ears, nose and rectum)

▪ SARS: Symptoms – fever, a dry cough, shortness of breath, or difficulty breathing. A person with SARS also may experience a headache, muscle aches, a sore throat, fatigue, and diarrhea. An older person may feel generally unwell (malaise) and lose his or her appetite but not have a fever.

▪ H1N1: Symptoms – cough, fever, sore throat, stuffy or runny nose, body aches, headache, chills, and fatigue


Diseases that cross form one species to another (Zoonosis)

▪ Transmission from one species to another does not happen often

▪ Conditions and opportunity must be jus right

▪ Many conditions must be met, a protein to protein match must occur for a virus to recognize a cell as a host cell

▪ Can also occur if two species are together long enough for a mutation to occur to the virus

▪ More common with bacteria and fungi

▪ Human Diseases that cross to animals are:

▪ Tuberculosis (bacteria), salmonella (bacteria), and ring worm (fungus)


Production of Monoclonal Antibodies

Polyclonal Response – A primary immune response

▪ A pathogen is typically recognized as many antigens

▪ Example: a virus protein coat (capsid) is made up of many proteins▪ For each protein there is an immune response and several kinds of plasma B cells undergo clonal

selection

▪ So different kinds of antibodies are produced

Many

Clone



Before how, here is why?

▪ Monoclonal antibodies are used to diagnose

▪ Pregnancy – early pregnancy the embryo produces a hormone called human chorionic gonadotropin (HCG)▪ HCG is only produced by the embryo, so only pregnant women have this hormone

▪ Hormone shows up in the blood and the urine of pregnant woman

▪ Hybridoma cells (hybrid cells we will discus next) can produce antibodies specific for HCG

▪ These anti HCG antibodies are chemically bonded to an enzyme that catalyzes a color change ▪ This is how a color change indicates pregnancy on a pregnancy test



Monoclonal Antibodies are antibodies of the same type.

▪ Produced by researchers

▪ Begins by injecting an antigen into a lab animal (like a mouse)▪ Antibodies will only respond to that antigen

▪ Animal given time to go through immune response

▪ Spleen then removed (harvested) to obtain blood cells▪ Some leucocytes cloned will be part of the blood cells

▪ B cells are kept alive by fusing them with cancerous (myeloma cells)▪ In the proper environment a few cells fuse together to form a hybrid cell called Hybridoma



▪ Hybridoma cells share characteristics of both cells (long lived like cancer cells)

▪ Produce specific antibody

▪ The entire mix of cells are transferred to an environment in which ONLY the hybridoma cells can survive

▪ Individual hybridoma cells now are cultured in separate containers

So Cool, Right?


Allergies

Allergic Response

▪ Occurs when a non-pathogen substance called an allergen, is encountered by certain leucocytes.

▪ Allergens include: pollen, peanuts, egg whites, and bee venom

▪ When first exposed to a particular allergen they produce a specific class of antibody called IgE (Immunoglobulin E)

▪ Then IgE binds to the antigen and trigger a response that leads to mast cell releasing a chemical called histamine

▪ Histamine – causes allergy symptoms, congestion, sneezing, itchy skin, red skin blotches, and even more serious like clsong the airway.

Movement

Endoskeletons & Exoskeletons

▪ Function of Skeletons:

▪ Support

▪ Protection

▪ Attachment points for muscles

▪ Endoskeleton – internal bones

▪ Exoskeleton - made of material called chitin, found on the outside of the animal

▪ Attachment points for muscles are found on the outside the bones for endoskeleton and on the inside of endoskeleton

▪ Exoskeletons also act like levers to maximize efficiency for a variety of movements▪ This gives insects incredible potential for strength and jumping ability

Movement

Endoskeletons & Exoskeletons

The bones of the endoskeleton of a human and those of the exoskeleton of an insect are similar enough to be given the same anatomical names

MovementMuscles Work in Antagonistic Pairs

▪ When a muscle contracts, one end of the muscle is connected to a bone (exoskeleton) is not designed to move.

▪ The other end of the same muscle is connected to a bone that is designed to move

▪ The immovable bone serves as an anchor

▪ Muscle can only shorten

▪ So muscles must work in pairs so that opposite motion of the bone can occur

Antagonistic Pairs – Muscles that accomplish opposite movements

MovementSynovial Joints Provide Limited Movements

▪ Synovial Joints are bone to bone joints

▪ Synovial Fluid – a lubricant contained in the capsule area of synovial joints

▪ Bones are also lined with cartridge to cushion bone to bone contact Synovial Fluid

Must be able to annotate a diagram of the elbow

Movement

A Muscle Fiber (book fibre)

▪ A muscle fiber is a muscle cell

▪ Three kinds:

▪ Smooth Muscle

▪ Cardiac Muscle

▪ Skeletal Muscle (Striated)

▪ Each muscle is made up of thousands of cells

▪ Muscle tissue also includes connective tissue, blood vessels, and nerves

▪ Muscle fibers contain multiple nuclei

▪ Sarcolemma – the plasma membrane of the muscle cells

▪ Transverse tubules (T- tubules) – tunnel-like extensions that penetrate the interior of the cell

Movement

A Muscle Fiber (book fibre)

Sarcoplasm – the cytoplasm of muscle fibers

▪ There a large number of organelles that store glycogen

▪ Remember glycogen is the way our muscles store glucose

▪ Myoglobin – a molecule that is similar to hemoglobin that stores oxygen

▪ Releases oxygen when muscle tissue is heavily used and oxygen supply becomes limited

▪ Many myofibrils run the length of the cell, parallel to each other

▪ Numerous mitochondria are found packed in between the myofibrils

▪ Supply ATP

▪ Sarcomeres – the contractile unit of the cell

▪ Contain the proteins Actin and Myosin

▪ Repeated patterns of sarcomeres in skeletal muscles give the striated pattern

Movement

Myofibrils and Sarcomeres

Myofibril is composed of many side by side contracting units called

sarcomeres

• One Sarcomere extends from Z line to Z line

• This is what you see when you see striations in skeletal muscle

• As Sarcomeres shorten muscle contracts

• These are repeated structures, they run the length of the muscle

• Muscle connected to tendon, tendon connected to bone, movement occurs

Movement

Myofibrils and Sarcomeres

▪ Myosin fibers are thick with head like structures

▪ Myosin can get shorter because it is one continuous protein within the sarcomere

▪ Actin is thin

▪ Is able to move within the sarcomere

▪ It is able to slide towards the center shortening the entire sarcomere

▪ Z lines get closer

▪ Both are made of proteins

▪ This is why meats are rich in protein

MovementSliding Filament Theory

▪ Motor neuron carries an action potential until it reaches the neuromuscular junction

▪ Acetylcholine is released into the synaptic gap between the neuron end buttons and the sarcolemma of the muscle fiber

▪ Acetylcholine binds to the receptors on the sarcolemma

▪ Sarcolemma ion channels open and sodium ions move through the membrane

▪ Resulting in action potential moving through the T tubules, causing the release of Calcium ions from the sarcoplasmic reticulum

▪ Released Ca ions flood into the sarcoplasm

▪ The myosin heads then attach to the binding sites on the actin

▪ The myosin heads all flex towards the center of the sarcomere

▪ The entire sarcomere shortens as the Z lines move towards each other

▪ ATP binds to the myosin head detaching the myosin from the actin, everything returns and waits for another action potential

▪ https://youtu.be/0kFmbrRJq4w

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https://youtu.be/0kFmbrRJq4w

MovementSliding Filament Theory

MovementTroponin & Tropomyosin

Tropomyosin – a thin protein filament that covers the binding site on actin when the muscle is not contracting

Troponin – another protein that binds to the tropomyosin at regular intervals along the length of the tropomyosin

▪ Troponin has binding sites for calcium ions

▪ When Ca floods the sarcoplasm it binds to the troponin which then stimulates the tropomyosin to slide uncovering the actin binding sites

▪ Myosin heads instantly bind to the actin binding site, leading to the shortening of the sarcomere

The KidneyOsmoregulation

▪ Metabolism – reactions within body cells

▪ These reactions create waste

▪ It is the job of the circulatory system to remove these waste

▪ Urea – a waste product from the metabolism of amino acids

▪ FYI – Those amino acids not used to make protein are removed from the body

▪ The body does not store amino acids

▪ Deamination – a chemical reaction in which the amine group (NH2)

▪ The amine group is incorporated into one of 3 types of waste:

▪ Ammonia

▪ Urea

▪ Uric Acid


▪ In mammals and other animals it is the kidneys job to filter out waste like urea

▪ Malpighian Tubule System – system used by insects to remove nitrogenous waste and osmoregulation

The KidneyEvolution

Nitrogenous Waste – the waste products that result from the deamination of amino acids

▪ Waste product contains nitrogen, thus the name

▪ A species ancestor that primarily used one of the 3 nitrogenous waste types than the emerging species will most likely use the same nitrogenous waste type

▪ Basically cannot evolve an entire new physiology even as they evolve into a new species

The KidneyEvolution

▪ Fish use ammonia – because of the habitat being water this highly toxic waste is diluted without the use of energy

▪ Terrestrial animals do not have that luxury

▪ Mammals produce urea – only toxic at very high levels

▪ Mammals can store urea in the bladder temporarily as urine

▪ Mammals system needs less water

▪ Birds and reptiles both use an egg that is self – contained for nutrients and water for development

▪ This separates birds and reptiles from the aquatic environments

▪ Big problem to solve ammonia cannot be stored in the egg (too toxic)

▪ Uric Acid – not as toxic and can be stored in the egg▪ Does take a lot of energy to produce

▪ Adult birds continue to produce uric acid - gives them independence from water

▪ Animals that produce ammonia or urea have to drink frequently compared to birds.

The KidneyEvolution

The KidneyEvolution

Nitrogenous Waste Excretion in Insects

▪ Insects have an open circulatory system.

▪ Insects blood is usually outside the blood vessels

▪ Malpighian Tubules – body cavities of insects that lie within the pools of blood.▪ They are closed on the distal end (away from the midline) and open into the insects gut the proximal

end (towards the midline)

▪ Nitrogenous waste, excess water and many salt ions remain in the tubules

▪ Useful substances are transported back into the pool of blood

▪ Waste is eliminated along with the feces

The Kidney

The Kidney

▪ The function of the kidney is to filter waste product from the blood

▪ Renal artery takes blood into each kidney

▪ Renal vein takes filtered blood back into circulatory system

▪ Urine is the fluid produced by the kidneys

▪ Consist of water and dissolved waste filtered from the blood stream

▪ Urine collects in the renal pelvis

▪ From Renal pelvis to ureter to urinary bladder

The Kidney

Nephron

▪ Filtering unit of the kidney

▪ A capillary bed called a glomerulus which filters various substances from the blood

▪ A capsule surrounding the glomerulus, called the Bowman’s capsule

▪ A small tube that extends from Bowman’s capsule consisting the proximal convoluted tubule, loop of Henle and distal convoluted tubule

▪ A second capillary bed called peritubular capillary bed, that surrounds the three-part tubule mentioned above

The Kidney

Bowman’s Capsule

▪ Each nephron contains a very small branch of the renal artery known as a afferent arteriole

▪ Brings unfiltered blood to the nephron

▪ Inside the Bowman’s capsule the afferent arteriole branches into a capillary bed called the glomerulus

▪ Fenestrations – very small slits on the wall of the glomerulus▪ Open when blood pressure increases

▪ This pressure comes from the efferent arteriole

The Kidney

Bowman’s Capsule

Ultrafiltration – the term used to describe the process by which various substances are filtered through the glomerulus under unusually high blood pressure in the capillary bed.

▪ Fluid that is ultra - filtered from the glomerulus passes through the basement membrane

▪ Prevents large molecules, like proteins, from becoming part of the filtrate

▪ Filtrate enters the proximal convoluted tubule

▪ Unfiltered blood exits via efferent arteriole

The Kidney

Bowman’s Capsule

▪ The body needs many of the substances in the filtrate.

▪ Things we can’t afford to lose:

▪ Water

▪ Salt ions

▪ Glucose

▪ Reabsorption occurs in the proximal convoluted tubule

▪ The wall is a single cell think

▪ They are taken back to the bloodstream via the peritubular capillary bed

• The proximal convoluted tubule is a single cell think.

• The interior of the resulting tube is called the lumen• The filtrate flows within

the lumen• Inner portions are lined

with microvilli to increase surface area

• Note mitochondria for active transport

• Reabsorbed molecules include Salt ions (Na+, Cl-, K+), Water, and Glucose


The body’s response mechanism that attempts to maintains homeostatic levels of water

▪ Water – the solvent of life (universal solvent)

▪ Water is eliminated in the urine each day

▪ The amount of water eliminated depends on:

▪ Total volume of water ingested

▪ Perspiration rate

▪ Ventilation/breathing rate

The Kidney

Loop of Henle

▪ Much of the water in the original filtrate remains after the filtrate has left the proximal convoluted tubule.

▪ Water and the remaining dissolved solutes enters the descending portion of the loop of Henle.

▪ This area is permeable to water but mostly impermeable to salt ions

▪ Then the filtrate enters the ascending portion of the loop of Henle

▪ This area is impermeable to water but permeable to salt ions

▪ As the filtrate moves up the ascending portion of the loop, salt ions are pumped out and enter the intercellular fluid.

The Kidney

Loop of Henle

▪ The loop of Henle of each nephron extends down into the medulla region of the kidney.

▪ Hypertonic – less water more solute

▪ Hypotonic – more water less solute▪ Water – solvent

▪ Water will always go from hypotonic to hypertonic

▪ Isotonic – equal water and solute

▪ The medulla area is hypertonic – so water moves out

▪ There is still enough water that the distal convoluted tubule is still relatively hypotonic

The KidneyAntidiuretic Hormone (ADH)

▪ The filtrate at the collecting duct is basically urine.▪ This is urine in the diluted form

▪ In most cases some of this excess water is reabsorbed through the walls of the collecting duct

▪ The collecting duct is differentially permeable to water

▪ Permeability depends on the presence or absence of ADH

▪ ADH is secreted in the posterior lobe of the pituitary gland and circulates around the body but targets the kidney’s collecting ducts

▪ If ADH is present the collecting duct becomes permeable to water and water moves by osmosis out of the collecting ducts and into the medulla interstitial fluid

▪ From there water enters the peritubular capillary bed thus returning to the blood stream

▪ ADH not present the collecting duct becomes impermeable to water

▪ Water then stays in the collecting duct along with various waste solutes and the urine is more dilute.

The KidneyAntidiuretic Hormone (ADH)

The Kidney

The KidneyAdaptation for Water Conservation

▪ Different organisms have adaptations for their environments

▪ Frogs and toad have almost no loops of Henle▪ They are basically unable to conserve water

▪ Their urine is always quite dilute

▪ A kangaroo rat that lives in the desert ▪ They recycle almost all of their water and lose very little

▪ They do this by having a long loop of Henle

▪ They have a large hypotonic area for water reabsorption using ADH

The KidneyComposition of Blood

▪ Blood entering the renal artery vs. blood leaving the kidney in the renal vein▪ In a healthy animal in the renal vein:

▪ A lowered amount of urea

▪ A lowered amount of salt ions (Na+, K+,Cl-)

▪ A lowered amount of water

▪ Nearly identical amount of glucose

▪ Nearly identical amount if protein

▪ No change in blood cells

The KidneyOsmoregulators and Osmoconformers

▪ The two types are most relevant to water-dwelling animals

Osmoregulators – animals that the internal tissues have a different solute concentration compared to their environment.

▪ These animals must have mechanisms to regulate water balance

▪ They expend a great deal of energy achieving this

▪ Most animals are osmoregulators

The KidneyOsmoregulators and Osmoconformers

Osmoconformers – are animals that have internal tissues that have virtually the same concentration as their environment

▪ They are said to be Iso-osmotic to their environment

▪ They do not need a mechanism to eliminate water, water moves freely

▪ Their environment is restricted to their own iso-osmatically match

The Kidney

Kidney Failure & Medical Issues

▪ When kidneys fail (two options):

▪ Option 1: Haemodialysis / kidney dialysis▪ This is when the patients blood is pumped into a device that contains a large

surface area of a membrane (dialysis machine)

▪ One side of the membrane is the patients blood and on the other side is a solution (dialysate)▪ Dialysate is similar to the chemical makeup to the patient’s blood but does not have urea

in it at the start.

▪ Urea is small enough to diffuse through the membrane and so slowly the urea leaves the blood and enters the dialysate

▪ The balance of water and some ions can also be regulated by adjusting which fluid on either side of the dialysis membrane has a greater concentration of each substance

▪ Kidney dialysis takes several hours each session and must be repeated every 1 -3 days

The Kidney

See page 477 Figure 11.21

The Kidney

Kidney Failure & Medical Issues

▪ Option 2: Kidney transplant ▪ Matching the donor is the key

▪ People can live with one kidney so it is possible for a close family member to donate a kidney

The Kidney

Testing Urine Composition

▪ Glucose

▪ There should be no urine in a healthy individual

▪ Blood Cells

▪ The glomerular filtrate should have no blood cells because blood cells are too large to fit

▪ Finding blood cells in the urine can be a sign of kidney malfunction or an infection

▪ Proteins

▪ There should be no proteins in the urine.

▪ Proteins are too large

▪ Drugs

▪ Drugs make there way through the blood stream and are filtered by the kidneys

The Kidney

Dehydration & Overhydration

Dehydration – too little water

Overhydration – too much water

▪ Normally water is lost by urine output, perspiration, and breathing

Dyhydration Overhydration

Sleepiness Change of behavior

Constipation Blurred vision

Dry mouth and skin Muscle cramps

Dizziness and headache Nausea and vomiting

Sexual Reproduction

Spermatogenesis

▪ The production of sperm cells by meiosis

▪ Spermatozoa (Sperm cells) are produced in the testes

▪ Spermatozoon singular

▪ Human male testes are located outside of the body because the sperm cells require cooler temperatures than inside the body

▪ Spermatogenesis occurs in the seminiferous tubules

Need to know also on page 481 11.23

Sexual Reproduction

Spermatogenesis

▪ Each spermatogonium (singular) undergo either mitosis or meiosis

▪ Spermatogonia undergo mitosis in order to replenish their numbers

▪ Spermatogonia undergo meiosis to produce spermatozoa

▪ AKA reduction division – because we go from diploid to haploid▪ Human 46 to 23 (23 homologous pairs to 23

individual chromosomes)

Sexual Reproduction

Spermatogenesis

▪ The steps of meiosis/spermatogenesis

▪ After meiosis the cells remain within the interior of the seminiferous tubule for a period of time as they mature to a mature spermatozoon

▪ Mature spermatozoa (differentiate to mature sperm cell) are moved to epididymis

Sexual ReproductionSpermatozoa

Sexual ReproductionOogenesis

▪ The production of female gametes by meiosis

▪ Oogenesis produces 4 cells like spermatogenesis

▪ 3 out of the 4 cells in this process are not used as gametes because they are too small to be viable

▪ These 3 cells are called polar bodies

▪ The fourth haploid cell produced is very large and is the ovum (ova – plural)

▪ Oogonia are cells within the ovaries that go through repeated mitosis

▪ This happens within the fetus

▪ Primary Oocytes are diploid

▪ Large number of oocytes begin the early stages of meiosis but the process stops during prophase 1

Sexual Reproduction

Oogenesis

▪ Also within the ovaries are follicle cells that undergo mitosis

▪ A single layer of follicle cells surrounds each primary oocyte. The entire structure is called the primary follicle

▪ The primary follicles remain unchanged till puberty

▪ During each menstrual cycle a few primary follicles finish meiosis 1

▪ Review reproduction cycle Topic 6

Sexual Reproduction

Sexual Reproduction

Sexual Reproduction

External & Internal Fertilization

▪ If a female animal lays eggs to allow the male to fertilize the eggs outside the female’s body, fertilization is then external

▪ The majority of fish reproduce via external fertilization

▪ Milt – fluid released by male fish that contains hundreds of sperm

Sexual Reproduction

External & Internal Fertilization

▪ Internal Fertilization – the female and male engaged in some form of intercourse in which spermatozoa are deposited into the female in order to fertilize one of more ovum.

▪ Animals that go through internal fertilizations have less offspring produced and show some sort of parental care of the young

Sexual Reproduction

Fertilization

▪ Humans:

▪ Resulting from sexual intercourse millions of spermatozoa are ejaculated into the female vagina

▪ Sperm absorb fructose from semen for energy

▪ Cervix separates the vagina and the uterus; some sperm makes it through

▪ They swim up the endometrial lining and some enter the Fallopian tubes

▪ If the female is near the middle of her menstrual cycle then there maybe a secondary oocyte within one or two of the Fallopian tubes▪ Millions of sperm are released only a few make the journey

Sexual Reproduction

Sexual ReproductionFertilization

▪ Fertilization occurs in one of the Fallopian tubes

▪ No one spermatozoon can accomplish the entire act of fertilization because it takes many spermatozoa to penetrate the zona pellucida (a glycoprotein gel layer of the secondary oocyte) and follicle cell layer

▪ Several spermatozoa gain access to the zona pellucida surrounding the secondary oocyte and release the hydrolytic enzyme contained in their acrosomes

▪ Acrosome Reaction

▪ One sperm will reach the plasma membrane first though, it will use hydrolytic enzymes of its acrosome to penetrate the egg

▪ Plasma membranes fuse together and the spermatozoon will donate the paternal set of haploid chromosomes to the maternal set.


Polyspermy – more than one spermatozoon fertilizing an ovum

▪ Results in multiple sets of chromosomes within the ovum

▪ Will not lead to a viable embryo


▪ Preventing polyspermy:

▪ Cortical Reaction – the steps that prevent cortical reaction▪ Within the cytoplasm of the ovum there are small vesicles called cortical granuales

▪ They are located all around the interior of the plasma membrane

▪ When the first spermatozoon and ovum fuse their plasma membranes the cortical granuals fuse with the ovum’s internal plasma membrane and release enzymes to the outside

▪ Enzyme causes changes in the zona pellucida making it impermeable to any more spermatozoa

▪ Happens a few seconds after the first spermatozoon gains access

▪ Ensures only one fertilizes the ovum

▪ Resulting fertilized ovum is referred to as a zygote▪ See page 487 figure 11.29

Sexual ReproductionEarly Development

▪ Fertilization stimulates the zygote to begin a mitotic division and the first division typically occurs 24 hours after fertilization

▪ Mitotic division continues all the way down the Fallopian Tube▪ The increasing as it goes

▪ It will be 100 cells by the time it reaches the uterus

▪ Blastocyst – the embryo by the time it gets to the uterus; it’s a hallow ball of cells

▪ Implantation –when the blastocyst sinks down in the endometrial tissue▪ As a result of implantation the embryo and the material endometrium soon begins to create a

structure known as the placenta

Sexual ReproductionRole of the placenta

Molecules passed from the fetus to the mother within the placenta

Materials passed from mother to fetus within the placenta

Carbon dioxide Oxygen

Urea Nutrients (glucose, amino acids, etc)

Water Hormones

Hormones Vitamins and minerals

Alcohol, nicotine, and other drugs if used by the mother during pregnancy

At no time does the blood from the mother and the fetus mix

Sexual Reproduction

Role of the placenta

▪ HCG – Human Chorionic Gonadotropin – secreted by the early hormone

▪ This is what EPT’s are designed to detect

▪ Main function is to maintain the corpus luteum of her ovary for a longer period of time when compared to the menstrual cycle

▪ The corpus luteum secretes progesterone that maintains the highly vascular endometrium▪ Progesterone - main function is to maintain the highly vascular endometrium

▪ Eventually the placenta takes over the production of progesterone during the pregnancy

▪ Oestrogen – among other things (next slide) stops the production of another oocyte

Sexual Reproduction

Progesterone Oestrogen

Helps maintain the highly vascular tissue characteristic of the uterus/placenta

Encourages muscle growth of the uterus

Suppresses contractions of the smooth muscle of the uterus (The uterus is highly muscular, for birth contractions)

Eventually "antagonizes” the action of progesterone to suppress uterine contractions

Stimulates mammary gland development late in pregnancy in preparation of milk production

Induces production of oxytocin receptors in uterine muscles late in pregnancy

Sexual Reproduction

Oxytocin

Positive Feedback – a cyclic process that can continue to amplify your bodies response to a stimulus until a negative feedback response takes over.

▪ In birth oxytocin is the main hormone for positive feedback

▪ Oestrogen is produced by the placenta is to induce production of oxytocin protein receptors in the uterine muscle

▪ Produced by the hypothalamus and secreted by the posterior pituitary gland

▪ When the time for birth has begun oxytocin is released into the bloodstream

▪ First contraction will stimulate more release of oxytocin, thus more contractions

▪ Having nothing to push on will cause the uterus to stop contracting

Documents

Animal Physiology Higher Level (HL). Antibody Production and Vaccination Fundamentals of the Immune System ▪ When a pathogen enters the body of any mammal