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Biology > Topic 11 - Further human health and physiology > Flashcards

Topic 11 - Further human health and physiology Flashcards

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1
Q

What are platelets?

A

Cell fragments that are essential in blood clotting. Platelets form in bone marrow, do not have nuclei, and have a lifespan of 8-10 days

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2
Q

Describe the process of blood clotting

A
  1. Damaged cells release chemicals which stimulate platelets to adhere to the damaged area. Then platelets adhere to each other forming a plug at the damaged area
  2. Clotting factors are released either from damaged tissue cells or from platelets
  3. The clotting factors set off a series of reactions in which the product of each reaction is the catalyst of the next reaction. This helps to ensure that clotting only occurs when it is needed and also quickens the process.
  4. Clotting factors convert inactive prothrombin to active thrombin. Thrombin catalyses the conversion of fibrinogen to fibrin.
  5. In the last reaction soluble fibrinogen is altered to insoluble fibrin. Fibrin is a fibre-like polypeptide that forms a net across the wound.
  6. The net of fibrin stablisises the platelet plug. Blood cells are caught in the net and form a clot. If exposed to air the clot dries to form a scab
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3
Q

What are the fundamental principles of immunity?

A
  1. Challenge and response
    - The immune system must be challenged by an antigen during the first infection in order to develop an immunity
    - All the cellular events are a part of the response which leads to immunity to a specific pathogen
  2. Clonal selection
    - Identification of the leucocytes that can help with a specific pathogen
    - Multiple cell divisions which occur to build up the needed number of B cells
  3. Memory cells
    - Cells that provide long-term immunity
    - Cells that remember a specific pathogen and how to produce the correct antibodies against it
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4
Q

What is active immunity?

A

The production of antibodies by the organism itself after the body’s defence mechanisms have been stimulated by antigens

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5
Q

What is passive immunity?

A

The acquisition of antibodies received from another organism, in which active immunity has been stimulated

e.g. vaccination, pregnancy, first milk

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6
Q

What are the stages in antibody production?

A
  1. Antigen presentation
  2. Activation of helper T-cells
  3. Activation of B-cells
  4. Production of plasma cells
  5. Production of memory cells
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7
Q

What happens in the stage of antigen presentation in antibody production?

A
  • Macrophages take in antigens by endocytosis, process them and attach them to membrane proteins called MHC proteins
  • MCH proteins carrying the antigens are moved to the plasma membrane by exocytosis
  • This way the antigens are displayed on the surface of the macrophage
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8
Q

What happens in the stage of activation of helper T-cells in antibody production?

A
  • Helper T-cells have receptors in their plasma membrane that can bind to antigens presented by macrophages
  • Each helper T-cell has receptors with the same antigent-binding domain as an antibody
  • These receptors allow the cell to recognise an antigen presented by a macrophage and bind to it
  • The macrophage pases a signal to the helper T-cell changing it from an inactive to an active state
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9
Q

What happens in the stage of activation of B-cells in antibody production?

A
  • Inactive B-cells have antibodies in their plasma membrane
  • If these antibodies match an antigen, the antigen binds to the antibody
  • An activated helper T-cell with receptors for the same antigen binds to the B-cell
  • The activated helper T-cell sends a signal to the B-cell, causing it to change from an inactive to an active state
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10
Q

What happens in the stage of production of plasma cells in antibody production?

A
  • Activated B-cells start to divide by mitosis to form a clone of cells
  • These cells become active, with a much greater volume of cytoplasm (known as plasma cells)
  • They have a very extensive network of rER
  • rER is used for synthesis of large amounts of antibody, which is secreted by exocytosis
  • Antibodies fight off infection
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11
Q

What happens in the stage of production of memory cells in antibody production?

A
  • Memory cells are B-cells and T-cells that are formed at the same time as activated helper T-cells and B-cells
  • The memory cells persist and allow a rapid response if the disease is encountered again
  • Memory cells give long-term immunity to a disease
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12
Q

How are monoclonal antibodies produced?

A
  1. Antigens that correspond to a desired antibody are injected into an animal
  2. B-cells producing the desired antibody are extracted from the animal
  3. Tumour cells are obtained. These cells grow and divide endlessly
  4. The B-cells are fused with the tumour cells, producing hybridoma cells that divide endlessly and produce the desired antibody
  5. The hybridoma cells are cultured and the antibodies that they produce are extracted and purified
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13
Q

How can monoclonal antibodies be used in diagnosing malaria?

A
  1. Monoclonal antibodies are produced that bind to antigens in malarial parasites
  2. A test plate is coated with the antibodies
  3. A sample is left in the plate long enough for malaria antigens in the sample to bind to the antibodies
  4. The sample is rinsed off the plate
  5. Any bound antigens are detected using more monoclonal antibodies with enzymes that cause colour change
  6. Can be used to measure the level of infection
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14
Q

How can monoclonal antibodies be used to treat anthrax?

A

Monoclonal antibodies are being developed which neutralise one of the toxins and therefore sustain the patient’s life until their immune system produces antibodies naturally

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15
Q

What is a vaccine?

A

A modified form of a disease-causing microorganism that stimulates the body to develop immunity to the disease, without fully developing the disease itself

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16
Q

What is the principle of vaccination?

A
  • Antigens in the vaccine cause the production of the antibodies needed to control the disease
  • Memory cells persist the antigens of the vaccine to give long-term immunity
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17
Q

What are the benefits of vaccination?

A
  1. Epidemics and pandemics can be prevente and some disease can be completely eradicated (smallpox and polio)
  2. Deaths due to disease can be prevented
  3. Disability due to disease can be prevented, decreasing health care costs
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18
Q

What are the dangers of vaccination?

A
  1. Toxic effects of mercury (neurotoxin) in vaccines
  2. Overload of the immune system due to multiple vaccines in a relatively short period of time
  3. Some vaccines may have a link to the onset of autism
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19
Q

What is the role of bones?

A
  • Provide a hard fram to support the body
  • Allow protection of vulnerable softer tissue and organs
  • Act as levers so that body movement can occur
  • Form blood cells in the bone marrow
  • Allow storage of minerals, especially calcium and phosphorus
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20
Q

What is the role of ligaments?

A
  • Tough, band-like structures that strengthen the joints
  • Provide stability for bones
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21
Q

What is the role of nerves?

A
  • Nerve endings in ligaments allow constant monitoring of the positions of the joint parts
  • Also help to prevent over-extension of the joint and its parts
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22
Q

What is the role of muscles?

A
  • Provide the force necessary for movement by shortening the length of their fibres/cells
  • Occur as antagonistic pairs
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23
Q

What is the role of tendons?

A
  • Attach skeletal muscles to bones
  • Cords of dense connective tissue
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24
Q

Draw a diagram of the human elbow joint

A
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25
Q

What is the funciton of cartilage?

A

Reduces friction and absorbs compression

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26
Q

What is the role of synovial fluid?

A

Lubricates the joint to reduce friction and provides nutrients to the cells of the cartilage

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27
Q

What is the role of joint capsule?

A

Surrounds the joint, encloses the synovial cavity, and unites the connecting bones

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28
Q

What is the role of biceps muscle

A

Contracts to bring about flexion (bending) of the arm

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29
Q

What is the role of triceps muscle?

A

Contracts to cause extension (straightening) of the arm

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30
Q

What is meant by diarthrotic joints?

A

Joints that can move freely

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31
Q

Compare the hip joint and the knee joint

A

Hip VS knee

  • freely movable VS freely movable
  • angular motion in many directions VS angular motion in one direction
  • rotational movement VS no rotational movement
  • ball-like structure in a cup-like depression VS convex surface in a concave surface
  • motions possible in hip joint: flexion, extension, abduction, adduction, circumduction, rotation
  • motions possible in knee joint: flexion and extension
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32
Q

What are the three types of muscle tissue in the body?

A
  1. Skeletal or striated
  2. Cardiac
  3. Smooth or non-striated
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33
Q

What are the main parts of striated (skeletal) muscle cells?

A
  1. Myofibrils
  2. Sacroplasmic reticulum
  3. Sacroplasm
  4. Sacrolemma
  5. Mitochondria
  6. Multiple nuclei
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34
Q

What are myofibrils?

A
  • Rod-shaped bodies that run the lenth of a muscle cell
  • Loads of cells closely packed and parallel to one another
  • Contractile elements of the muscle cells
  • Reason to striated muscles’ banded pattern (light and dark)
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35
Q

What is sacroplasmic reticulum?

A
  • A fluid-filled system of membranous sacs surrounding the muscle myofibrins
  • Much like smooth endoplasmic reticulum
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36
Q

What is sacroplasm?

A
  • The cytoplasm of muscle fibres
  • Contains large numbers of glycosomes that store glycogen
  • Has large amounts of a red-coloured protein called myoglobin
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37
Q

What is the sacrolemma?

A
  • The plasma membrane of muscle fibres
  • Has multiple tunnel-like extensions that penetrate the interior of the cell called transverse or T tubules
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38
Q

What is special about muscle cells’ nuclei?

A

Each muscle fibre has multiple nuclei that lie just inside the plasma membrane

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39
Q

What is a sacromere?

A

The building blocks of myofibrils and the units that enable movement

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40
Q

Draw and label the structure of a sacromere

A

tba

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41
Q

What are the three types of bands in sacromeres?

A

Z, A, H, M and I

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42
Q

Describe the bands in the structure of sacromeres

A
  1. Z lines
    - mark the ends of the sacromere
  2. A bands
    - dark in colour
    - extend the entire length of the myosin filaments
  3. H band
    - narrow
    - occurs in the middle of the A band
    - contains only myosin, no actin
  4. M line
    - occurs in the middle of the H band
    - a protein that holds the myosin filaments together
  5. I band
    - light in colour
    - contain only actin, no myosin
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43
Q

Draw a diagram of the structure of a sacromere

A
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44
Q

Draw the structure of the bands in a sacromere

A
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45
Q

Describe actin filament

A
  • Thin filaments (8 nm)
  • Contains myosin-binding sites
  • Individual molecules form helical structures
  • Includes two regulatory proteins, tropomyosin and troponin
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46
Q

Describe myosin filament

A
  • Thick filaments (16 nm)
  • Contains myosin heads that have actin-binding sites
  • Individual molecules form a common shaft-like region with outward protruding heads
  • Heads are referred to as cross-bridges and contain ATP-binding sites and ATPase enzymes
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47
Q

What are the stages of muscle contraction (sliding filament theory)?

A
  1. A motor neuron carries an action potential until it reaches a neuromuscular junction
  2. A neurotransmitter called acetylcholine is released into the gap between the axon terminal and the sacrolemma of the muscle fibre
  3. The acetylcholine binds to receptors on the sacrolemma
  4. Sacrolemma ion channels open and sodium ions move through the membrane
  5. This generates a muscle action potential
  6. The muscle action potential moves along the membrane and through the T tubules
  7. After generation of the muscle action potential, the acetylcholine is broken down by an enzyme called acetylcholinesterase. This ensures that one nerve action potential causes only one muscle action potential
  8. The muscle action potential moving through the T tubules causes release of calcium ions from the sacroplasmic reticulum. The calcium ions flood into the sacroplasm
  9. The calcium ions bind on troponin on the actin myofilaments. This exposes the myosin-binding sites
  10. The myosin heads include ATPase which splits ATP and releases energy (step 1 on figure)
  11. The myosin heads then bind to the myosin-binding sites on the actin with the help of the protein called tropomyosin (step 2)
  12. The myosin-actin cross-bridges rotate toward the centre of the sacromere. This produces power or working stroke (step 3)
  13. ATP once again binds to the myosin head rsulting in the detachment of myosin from the actin (step 4)
  14. If there are no further action potentials, the level of calcium ions in the sacroplasm falls. The troponin-tropomyosin complex moves to its original position, thus blocking the myosin-binding sites. The muscle relaxes
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48
Q

What is excretion?

A

The removal from the body of the waste products of metabolic pathways

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49
Q

What is osmoregulation?

A

The control of the water balance of the blood, tissue, or cytoplasm of a living organism

50
Q

Draw and label a diagram of the kidney

A
51
Q

Draw a diagram of a single nephron and describe the function of each part

A
  • A capillary bed (glomerulus) filters various substances from the blood
  • A capsule called Bownman’s capsule surrounds the glomerulus
  • A small tube that extends from Bowman’s capsule (three parts):
    1. proximal convoluted tube
    2. loop of Henle (descending and ascending limb)
    3. distal convoluted tubule
  • A second capillary bed called the peritubular capillary bed which surrounds the three-part tubule mentioned above (not visible in diagram)
52
Q

Draw a diagram of a glomerulus

A
53
Q

Describe how the function of a glomerulus supports ultrafiltration

A
  • A small branch of the renal artery (afferent arteriole) brings unfiltered blood to the nephron
  • The afferent arteriole branches into a capillary bed called the glomerulus
  • The walls of the capillaries have fenestrations (small slits) that open when blood pressure is increased
  • Blood pressure increases because the efferent arteriole has a smaller diameter than the afferent arteriole → pressure increases
54
Q

Outline the process of ultrafiltration

A
  • Process by which various substances are filtered through the glomerulus
  • The fluid which is ultrafiltered passes through the basement membrane, which helps prevent large molecules (proteins, blood cells etc) from becoming a part of the filtrate
  • The filtrate enters the proximal convoluted tubule
  • Blood cells, proteins, and other molecules which did not become a part of the filtrate exit the Bowman’s capsule through the efferent arteriole
55
Q

Describe the structure of the proximal convoluted tubule

A
  • The tubule is only one cell thick
  • Composed of a ring of cells
  • The interior (lumen) has microvilli to increase the surface area for reabsorption
56
Q

How are glucose, water, and salts reabsorbed in the proximal convoluted tubule?

A
  • Absorbed through osmosis and active transport
    1. Salt ions
  • Actively transported into the tubule cells and then into the intercellular space
  • Absorbed by the peritubular capillary bed
    2. Water
  • The movement of salt ions induces water to follow the same route by osmosis
    3. Glucose
  • All glucose is absorbed
  • Only transport that can absorb all the glucose is active transport
57
Q

What is the role of the loop of Henle in maintaining the water balance of the blood?

A
  • The descending limb is relatively permeable to water and relatively impermeable to salt ions → water leaves the tubule
  • The ascending limb is relatively impermeable to water and permeable to salt ions → sodium ions are pumped out and enter the intercellular fluid
  • The loop extends down into the medulla region
  • The filtrate that moves into the distal convoluted tubule is still relatively hypotonic (lots of water)
58
Q

What are the roles of ADH and the collecting duct in maintaining the water balance of the blood?

A
  • All of the wanted solutes have been reabsorbed at this point
  • The collecting duct is differentially permeable to water → depends on the presence or absence of antidiuretic hormone (ADH)
  • ADH is secreted from the pituitary gland
  • The target tissue of ADH is the kidney collecting ducts
  • When ADH is present, the collecting duct becomes permeable to water → water moves out by osmosis and enters the capillary bed
  • When ADH is not present, the collecting duct becomes impermeable to water
59
Q

Which gland secretes antidiuretic hormone (ADH)?

A

The pituitary gland

60
Q

What is meant by blood plasma in the kidney?

A

The blood that enters the glomerulus. Reabsorption and filtering have not occurred yet

61
Q

What is meant by glomerural filtrate?

A

The fluid (filtrate) which enters the proximal convoluted tubule after ultrafiltration. No reabsorption has occurred yet

62
Q

What is meant by urine?

A

The filtrate that has undergone filtration, reabsorption, and osmoregulation and is taken to the bladder for elimination

63
Q

What are the concentrations of proteins, glucose, and urea in blood plasma, glomerular filtrate, and urine?

A

Proteins:

  • Lots in blood plasma
  • None in glomerular
  • None in urine

Glucose

  • Lots in blood plasma
  • Lots in glomerular
  • None in urine

Urea

  • Little in blood plasma
  • Little in glomerular
  • Lots in urine
64
Q

Explain the concentrations of proteins, glucose, and urea in blood plasma, glomerular filtrate, and urine

A
  • Proteins are too large to fit through the basement membrane within the glomerulus → not a part of the filtrate or urine
  • Glucose becomes a part of the filtrate but active transport in the proximal convoluted tubule takes 100% of the glucose back → no glucose in urine
  • Urea is in low concentration at first but then most of the water is removed → urea concentration increases
65
Q

Why is glucose present in the urine of untreated diabetes patients?

A
  • Glucose level of diabetics is unusually high
  • Active transport in the proximal convoluted has a maximum rate at which they can work
  • If the maximum threshold of concentration of glucose is exceeded, the transport can’t keep up
  • Active transport in diabetics is unable to move all the glucose back into the bloodstream → some glucose remains in the urine
66
Q

Draw a diagram of human seminiferous tubule (testis tissue)

A
67
Q

What is the function of interstitial cells (Leydig cells)?

A

Produce and secrete testosterone

68
Q

What is the function of germinal epithelium cells?

A

To divide endlessly by mitosis to produce more diploid cells to produce eventually haploids

69
Q

Where are interstitial (Leydig) cells located?

A

Between seminiferous tubule sections

70
Q

What are spermatozoa?

A

Mature spermatids, sperm cells

71
Q

What are Sertoli cells?

A

Provide nutrients for the spermatids

72
Q

What are the stages of spermatogenesis?

A
  1. Mitosis
  2. Cell growth
  3. Meiosis I
  4. Meiosis II
  5. Cell differentiation
    (6. Detaching)
73
Q

What happens in the mitosis of spermatogenesis?

A

The germinal epithelium cells divide endlessly by mitosis to provide enough diploid cells to produce sperm

74
Q

What happens in the cell growth of spermatogenesis?

A

The germinal epithelium cells grow larger and become primary spermatocytes

75
Q

What happens in the meiosis(es) of spermatogenesis?

A
  • Each primary spermatocyte carries out meiosis I to produce two secondary spermatocytes
  • Each secondary spermatocyte carries out meiosis II to produce two spermatids
76
Q

What happens in the cell differentiation of spermatogenesis?

A
  • Spermatids become associated with Sertoli cells and develop into spermatozoa through cell differentiation
  • Spermatids grow flagella for motility and acrsosomes to contain enzymes necessary for fertilisation
77
Q

What is the role of leutenising hormone (LH) in spermatogenesis?

A

It stimulates Leydig cells to produce testosterone

78
Q

What is the role of testosterone in spermatogenesis?

A

Stimulates the meiotic divisions of spermatogonia into spermatozoa together with follicle stimulating hormone (FSH)

79
Q

What is the role of follicle stimulating hormone (FSH) in spermatogenesis?

A

Stimulates the meiotic divisions of spermatogonia into spermatozoa together with testosterone

80
Q

Draw the structure of the ovary

A
81
Q

What are the stages of oogenesis?

A
  1. Mitosis
  2. Cell growth
  3. Meiosis I
  4. Unequal division of cytoplasm
  5. Meiosis II
  6. Ovulation
  7. Degeneration
82
Q

What happens in the mitosis of oogenesis?

A

The germinal epithelium cells divide by mitosis to form more diploid cells for haploid production

83
Q

What happens in the cell growth of oogenesis?

A

The diploid cells grow into larger cells called primary oocytes

84
Q

What happens in the meiosis I of oogenesis?

A
  • The primary oocytes start meiosis I but stop at prophase I
  • The primary oocyte and a single layer of follicle cells around it form a primary follicle
85
Q

What happens in the unequal division of cytoplasm of oogenesis?

A
  • A few primary follicles start to develop
  • The primary oocyte completes meiosis I forming two haploid nuclei
  • The cytoplasm of the primary oocyte is divided unequally forming a large secondary oocyte and a small polar cell
86
Q

What happens in the meiosis II of oogenesis?

A
  • The secondary oocyte starts meiosis II but stops in prophase II
  • The follicle cells proliferate and follicular fluid forms
87
Q

What happens in the ovulation of oogenesis?

A

The mature follicle bursts releasing the egg

(The egg is actually still a secondary oocyte)

88
Q

What happens in the degeneration of oogenesis?

A

The first and second polar bodies do not develop and degenerate

89
Q

What happens to the secondary oocyte after it has been fertilised?

A

It completes meiosis II to form an ovum and a second polar cell

90
Q

Draw a mature sperm

A
91
Q

Draw a mature egg

A
92
Q

What is the role of the epididymis in semen production?

A

Sperm cells are stored and gain motility

93
Q

What is the role of the seminal vesicle in semen production?

A
  • Add a large volume of fluid (70%)
  • Fluid has a high concentration of fructose, a high-energy carbohydrate needed to provide the energy for the sperm cells to swim to the ovum
94
Q

What is the role of the prostate gland in semen production?

A
  • Adds 30% of the semen fluid
  • The fluid is alkaline and helps the spermatozoa survive the environment within the acidic vagina
95
Q

How is the structure of a sperm cell specialised for its function?

A
  • Very small and light
  • Has a flagellum for motility
  • Mitochondria to provide ATP for swimming
  • An organelle called an acrosome contains hydrolytic enzymes which help with the fertilisation process
  • Do not contain any unnecessary organelles or structures
96
Q

How is the structure of an egg cell specialised for its function?

A
  • Largest cell in the body
  • Unequal division ensures that there is lots of cytoplasm, nutrients, and organelles
  • Contains vesicles called cortical granules which function after fertilisation
  • Outside the plasma membrane is a layer of glycoproteins called zona pellucida that has a function during fertilisation
  • A layer of hundreds of follicle cells outside the cell for protection
97
Q

Compare spermatogenesis and oogenesis

A

Spermatogenesis VS oogenesis

  • millions of gametes per day VS one gamete per month
  • four gametes for each germinal cell VS one gamete for each germinal cell
  • very small gametes VS very large gametes
  • occurs within testis VS within ovaries
  • gametes released during ejaculation VS released during ovulation
  • haploid nucleus from meiosis VS haploid nucleus from meiosis
  • continues through whole life VS starts at puberty, occurs every month and stops during menopause
98
Q

What are the stages of fertilisation?

A
  1. Arrival os sperm
  2. Binding
  3. Acrosome reaction
  4. Fusion
  5. Cortical reaction
  6. Mitosis
99
Q

What is meant by acrosome reaction in fertilisation?

A
  • Several sperm cells reach the egg cell and penetrate the follicle cell layer
  • The sperm cells reach the zona pellucida (glycoprotein gel layer)
  • The sperms release the hydrolytic enzymes contained in their acrosomes
  • Acrosome enzymes allow cell membranes of sperm and egg to meet and fuse together
100
Q

What happens in the cortical reaction of fertilisation?

A
  • Is initiated after the two gametes fuse together
  • The cortical granules fuse with the oocyte’s cell membrane and release their enzymes to the outside
  • The enzymes result in a chemical change in the zona pellucida making it impermeable to sperm cells
  • Takes place withing a few seconds after the first sperm comes through the zona pellucida
101
Q

When is the secondary oocyte referred to as a zygote?

A

After cortical reaction has occurred and the cell has completed meiosis II

102
Q

What is the role of human chorionic gonadotrophin (HCG) in early pregnancy?

A
  • Enters the bloodstream of the mother
  • Target tissue is the corpus luteum
  • Acts to maintain the secretory functions of this gland longer than the typical menstrual cycle
  • Corpus luteum continues to secrete both estrogen and progesterone → the endometrium is maintained
103
Q

Where is human chorionic gonadotrophin (HCG) produced?

A

Produced and secreted by the embryo

104
Q

Outline the early embryo development (before implantation)

A
  • The cell first divides about 24 hours after fertilisation
  • During the first 5 days the embryo is dividing by mitosis and moving within the Fallopian tube
  • The rate of mitotic divisions increases
  • By the time the embryo reaches the uterus it is around 100 cells and ready to implant
  • The embryo is a hollow ball of cells and is called a blatocyst
105
Q

Describe the blatocyst

A
  • A surrounding layer of cells called the throphoblast
  • A group of cells on the interior known as the inner cell mass and located toward one end of the ball, will become the body of the embryo
  • A fluid-filled cavity
106
Q

Describe the structure of the placenta

A
  • A disc-shaped structure
  • Placental villi
  • Inter-villous spaces
107
Q

What is the function of placental villi?

A

To provide a large surface area for gas exchange and exchange of other materials. Fetal blood flows through capillaries in the villi

108
Q

What is the function of the inter-villous spaces in the placenta?

A

Maternal blood flows through these spaces, brought by uterine arteries and carried away by uterine veins

109
Q

What is the role of the placenta in the hormonal control of pregnancy?

A
  • By the middle of the pregnancy, the corpus luteum degenerates and can no longer secrete estrogen and progesterone
  • Cells in the placenta start secreting estrogen and progesterone instead and continue secreting until the end of the pregnancy
110
Q

Does maternal blood flow along the umbilical cord and through the fetus?

A

No

111
Q

What is provided by the mother to the fetus?

A
  1. Oxygen
  2. Glucose
  3. Lipids
  4. Water
  5. Minerals
  6. Vitamins
  7. Antibodies
  8. Hormones
112
Q

What is given away from the fetus to the mother?

A
  1. Carbon dioxide
  2. Urea
  3. Hormones
  4. Water
113
Q

What is chorion in the placenta?

A

Forms the placental barrier and controls what passes in and out of the placenta

114
Q

What does the cytoplasm of chorion in the placenta do?

A

Produced estrogen and progesterone and secretes them into the maternal blood

115
Q

How is the structure of the placenta specialised in exchanging materials?

A
  • Materials exchanged through active transport (mitochondria in the chorion provide ATP)
  • Small distance between maternal and fetal blood
  • Capillary carrying fetal blood is close to the villus surface
116
Q

What is the role of the amniotic sac and amniotic fluid?

A

To support and protect the fetus

117
Q

What is responsible for exchanging materials between the maternal and fetal blood?

A

The placenta

118
Q

What happens to the progesterone level at the end of pregnancy?

A

It falls

119
Q

What hormone is secreted at the end of pregnancy after progesterone level has fallen?

A

Oxytocin

120
Q

What does oxytocin do?

A

Causes the muscle in the uterus wall to contract

121
Q

How is positive feedback apparent in childbirth?

A

Oxytocin stimulates the uterus wall muscle to contract, which simulates the secretion of more oxytocin, which stimulates the uterus wall muscle to contract again → contractions become stronger each time

122
Q

What happens after the uterus starts to contract?

A
  • The contractions get stronger
  • The cervix relaxes and becomes wider
  • The amniotic sac bursts and the amniotic fluid is released
  • The baby comes out through the cervix and the v
  • The placenta is expelled the same way after a while

Biology (13 decks)

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