Group 5 - Mammary glands and Lactation

Question 1

Mammary Glands: From which tissue do they originate from?

Answer 1

the epidermis

Question 2

Mammary Glands: Pre-natal Mammogenesis
- describe the pre-natal mammogenesis 5

Answer 2

the mammary ridges are thickened epidermal tissue

the mammary ridges give rise to the primary mammary bud

the primary mammary buds push into the dermis to grow

they primary mammary buds branch as they grow into the dermis forming secondary mammary buds

the secondary mammary buds form a cap of myoepithelial cells and form lactiferous ducts

Question 3

Mammary Glands: Where do these glands arise?
- Where are the mammary ridges located?

Answer 3

they arise along 2 mammary ridges on the ventral surface of the developing foetus

the mammary ridges extend from the axillary region to the inguinal region

Question 4

Mammary Glands: Microanatomy
- Describe the anatomy of each alveolus 2
- How does milk move out of the alveolus and into the ducts?

Answer 4

consists of epithelial cells surrounding a spherical lumen

myoepithelial cells surround each alveolus and the ducts

by contraction of the myoepithelial cells propelling the milk out of the alveoli and into the ducts

Question 5

Mammary Glands: Macroanatomy
- Describe the anatomy of lobes 5

Answer 5

groups of alveoli form lobules
each lobule consists of around 200 alveoli
each lobule is surrounded by connective tissue
groups of lobules form lobes
each lobe is surrounded by connective tissue

Question 6

Mammary Glands: Describe the path of milk coming out of a lobe 4

Answer 6

milk enters a small milk duct
several small milk ducts drain into a large milk duct
the large milk duct drains into a gland cistern
the gland cistern drains into a teat cistern

Question 7

Mammary Glands: Why is the teat streak white in appearance?
- Why is it needed?

Answer 7

due to keratin

it is bacteriostatic so helps prevent bacteria entering the teat from the environment

Question 7

Mammary Glands: For dogs, how many glands supply each teat?
- What about for cows?
- What about for horses?

Answer 7

multiple

1

2

Question 8

Mammary Glands: What name is given when there is an extra teat?

Answer 8

polythelia

Question 9

Mammary Glands: In ruminants, which ligaments support the mammary gland (udder)?

Answer 9

medial suspensory ligament
lateral suspensory ligaments

Question 10

Mammary Glands: ruminants
- Where does the Medial Suspensory Ligament arise from?
- Describe its structure
- where does the Lateral suspensory ligament run?
- Describe its structure

Answer 10

the symphyseal tendon

elastic connective tissue

from the symphyseal tendon and over the lateral aspect of the udder

inelastic connective tissue

Question 11

Mammary Glands: what type of growth is seen from birth to puberty?
- What type of growth is seen after puberty?
- What is happening? 3

Answer 11

isometric growth

allometric growth

rapid growth of ducts occurs in the presence of prolactin and growth hormone
ducts begin to branch under the influence of oestrogen during the oestrus cycle
alveoli are formed under the influence of progesterone

Question 12

Mammary Glands: What happens to mammary growth during pregnancy? 2

Answer 12

terminal alveoli grow into lobules due to progesterone dominance
prolactin, adrenal cortical hormones and placental lactogen allow the synthesis of milk

Question 13

Mammary Glands: What happens with each lactation up until the 4th lactation? 3

Answer 13

after lactation, there is a greater baseline of tissue mass than the previous lactation
so there is more secretory tissue present for each lactation
so milk production increases with each lactation

Question 14

Mammary Glands: What action does Placental Lactogen have during pregnancy?
- which cells of the placenta produce it?
- hence which is the main species this hormone is seen in?

Answer 14

it has both prolactin and growth hormone activities

binucleate cells

sheep

Question 15

Mammary Glands: When does the mammary gland start producing milk?
- has all the alveolar growth finished by parturition?
- Why is this advantageous?

Answer 15

at parturition

no mammary growth continues for a few weeks after parturition

the tissue development increases as the biomass of the neonate increases
this enables milk production to meet the increasing demand of the growing neonate

Question 16

Mammary Glands: Vascularisation
- For thoracic glands, where have the mammary arteries branched off?
- What about for Abdominal glands?
- What about for inguinal glands?

Answer 16

internal thoracic artery

cranial and caudal superficial epigastric arteries

external pudendal artery

Question 17

Mammary Glands: Lymph Drainage
- How does lymph drainage work for mammary glands? 3
- How is this clinically relevant? 3

Answer 17

the cranial glands drain to the axillary lymph nodes
the caudal glands drain to the superficial inguinal lymph nodes
the muddle glands drain to either cranially or caudally

a tumour on the left hand side is unlikely to spread to the right hand side
caudal glands will metastasise caudally
cranial glands will metastasise cranially