Group 3- set 2/3- Placental Function - revision period - COMPLETE **** Flashcards
State 6 functions of the placenta
delivery of gases
delivery of nutrients
energy storage
excretion of waste products
placental derived hormones
barrier to toxic substances
State the overall pattern of growth of the placenta and foetus during pregnancy
- What does this indicate about the placenta?
- How is this enabled?
most placental growth occurs in the first half of pregnancy
most foetal growth occurs in the last trimester of pregnancy
that placental efficiency must increase with gestation in order to support the foetus
increased uterine and umbilical blood flow
Nutrient and Gaseous Exchange: How so many substances transfer from maternal to foetal blood?
- State 5 factors which influence this process and explain why
by passive diffusion
blood flow
structure influences the area for exchange
morphology influences the number of tissue barriers against the exchange
electrical gradient - a slight negative charge encourages positive charged ions to diffuse across
concentration gradient for exchange between maternal and foetal blood
Which types of placenta, in terms of morphology (layers of tissue) are most efficient for exchange of substances? - state them in order of most efficient to least efficient
haemochorial
endotheliochorial
epitheliochorial
How are amino acids and glucose transferred to foetal blood?
- if done by active transport, how does this work?
passively and by active transport
specific carrier molecules for amino acids and glucose work to move these molecules against the concentration gradient from maternal to foetal blood
Endocrine Placenta: Give the hormones produced by the placenta
progesterone
oestradiol
prolactin
relaxin
placental lactogen
Endocrine Placenta - Progesterone: What other structure produces progesterone for a portion of pregnancy?
- What stimulates the placenta to start secreting progesterone?
the corpus luteum
the production of LH, prolactin and oestrogens
Endocrine Placenta - Progesterone: What is the function of Progesterone during pregnancy? 3
- What would a progesterone antagonist do?
suppress myocetrial contractility
stimulate production of histotroph
stimulate mammary gland development
induce abortion
Progesterone Profiles: Explain why progesterone secretion is not simple during pregnancy 2
the corpus luteum is the source of progesterone for the first part of pregnancy
but in some species the placenta will take over progesterone production
State the gestation length and time for placental progesterone ‘take over”:
- Bitch
- Queen
- Rabbit
- Goat
65 days and no placental takeover
65 days and no placental takeover
30 days and no placental takeover
150 days and no placental takeover
State the gestation length and time for placental progesterone ‘take over”:
- Sow
- Cow
- Ewe
- Mare
114 days and no placental takeover
283 days and between days 150-240
145 days and on day 50
330 days and between days 140-210
For species with no placental takeover, what is the significance of this? 2
it means that the corpus luteum is the only source of progesterone
so if the corpus luteum is removed at any time during pregnancy the pregnancy will be terminated
Endocrine Placenta: Oestrogens
- Is Oestradiol the only type of oestrogen produced during pregnancy? 3
no, humans produce oestriol
ruminants produce oestrogen
horses produce equine specific oestrogens
Endocrine Placenta: Oestrogens
- What is their function? 5
stimulate placental growth
stimulate myocetrial growth
stimulate mammary development
increase uterine blood flow
preparation for parturition
Endocrine Placenta: Prolactin
- Other than the placenta, where else is prolactin produced?
- What can prolactin secretion be stimulated by?
- What can prolactin secretion be inhibited by?
the anterior pituitary gland
oestradiol
dopamine
Endocrine Placenta: Prolactin
- What are the functions of Prolactin? 3
stimulates lobuloalveolar growth and locatogenesis in the mammary gland
stimulates maternal behaviour
stimulates progesterone production from the corpus luteum of dogs and rodents
Endocrine Placenta: Relaxin
- Where is relaxin produced?
- Do cattle secrete relaxin?
by the corpus luteum in sow
by placenta in bitch queen mare rabbit
no but relaxin-like factor is produced which is an equivalent hormone
Endocrine Placenta: Relaxin
- What are the functions of Relaxin? 3
softening of connective tissue enabling growth of foetus
relaxation of pelvic ligaments
role in parturition
Endocrine Placenta: Relaxin
- What is the significance of relaxin in dogs and cats?
it can be used to diagnose pregnancy
Endocrine Placenta: Placental Lactogen
- Which hormone is placental lactogen similar to and in what way?
- Where is it produced?
- Where is it released into?
prolactin
placental lactogen binds to prolactin receptors
binucleate cells of the placenta in ruminants
maternal and foetal circulation
Endocrine Placenta: Placental Lactogen
- What is its function? 2
modulates foetal metabolism
stimulates mammary gland development
Endocrine Placenta: State other specific placental hormones in Ruminants that could be sued for pregnancy diagnosis in cattle
- Why are these specific to ruminants?
pregnancy specific protein B PSPB
pregnancy associated glycoprotein PAG
because they are produced by binucleate cells
Endometrial Cups: When do the equine endometrial cups start appearing?
- What do they do?
about day 40
produce equine chorionic gonadotrophin
Endometrial Cups: These cups produce ECG
- How does ECG behave?
- What is its function? 2
- What happens eventually to the accessory corpus luteums?
like FSH and LH
it increases progesterone secretion form the primary corpus luteum for a short period of time
it then induces the formation of an accessory corpus luteums
their activity will decrease and plasma progesterone levels will decrease
Endometrial Cups: After the accessory corpus luteums activity ceases, how is progesterone maintained for the remainder of pregnancy?
- but how is this possible if there is such a drop in progesterone concentration of the progesterone profile?
by placental progestogens
unique progestogens are made which act locally
Unique Progestogens in the mare: State the main Progestogen
5-alpha-pregnane
Pregnant Bitch: Compare the luteal phase between pregnant and non-pregnant bitch
- What main hormones does the placenta produce in low levels?
- What is the corpus luteal progesterone secretion dependent on?
there is a prolonged luteal phase in both
oestrogens and progestogens
LH and prolactin
Pregnant Bitch: When can you separate progesterone profile from non-pre and pregnant bitch and how?
at day 21 there will be a rapid rise in progesterone in the pregnant bitch divergent from the non-pregnant profile
Effects of Prostaglandin: When would the administration of Prostaglandin F2 alpha be effective in terminating a pregnancy of the following species:
- Cow
- Ewe
- Sow
- Mare
- Goat
- Bitch
- Queen
up to day 150
up to day 45
throughout pregnancy
up to day 35
throughout pregnancy
throughout pregnancy
throughout pregnancy
