Reproduction - mammary gland and lactation

Question 1

What is the streak canal?

Answer 1

Keeps milk in and bacteria out

Question 2

What is the teat cistern?

Answer 2

Ducts in the teats.

Separated from the streak canal by Fursteberg Rosette.

Has a capacity for 30-45ml

Question 3

What is the gland cistern?

Answer 3

Another duct, separated from the teat cistern by Cricoid fold.

Has a capacity for 400ml

Question 4

What the stroma?

Answer 4

Connective tissue containing fibroblasts, adipocytes, plasma cells and blood vessels

Question 5

What is the parenchyma?

Answer 5

A functional glandular part iwth alveoli and ducts

Question 6

What are the units of the parenchyma?

Answer 6

Alveoli
Lobe
Gland cistern
Galatophore
Ducts

Question 7

What are the alveoli?

Answer 7

Small bilk shape structure with a hollow centre lined with epithelial cells secreting milk. Each bulb is surrounded by a network of capillaries and myoepithelial cells (to contract)

Question 8

What the median suspensory ligament?

Answer 8

Divides the left and right halves of the udder, connecting to the abdominal walls.

Contains lamellae fibres and elastic tissue that is responsive to the milk weight in the udder

Question 9

What is the lateral suspensory ligament?

Answer 9

Inflexible, surrounds outer udder wall and attaches to prepubic and subpubic tendons

Question 10

What is the intermammary groove?

Answer 10

Where the median and lateral suspensory ligaments meet

Question 11

What is the vasculature of the udder?

Answer 11

Blood enters via two external pubic arteries

Mammary artery branches, cranial and caudal. Protected by a sigmoid flexure for tissue stretch

Blood exits via external pudic veins or the milk veins (subcutaneous abdominal veins)

Question 12

What is the cellular mechanism of milk synthesis?

Answer 12

1. Exocytosis of small proteins go into the alveoli lumen
2. Cholesterol and fatty acids turn into triglycerides, surrounding the membrane stopping fat globules
3. Transmembrane secretion of ions and water
4. Transcytosis of extra alveolar proteins, such as immunoglobulins, hormones and albumin from the intersitial space
5. Paracellular pathways to transfer milk

Question 13

What is mammogenesis?

Answer 13

The development of mammary tissue.

1. Paired mammary ridges of thickened epidermal tissue develops on the ventral surface of the embryo
2. At week 7-8 tissue develops inwards, penetrating mesenchyme forming mammary buds. This branches into another bud forming a canal
3. Controlled by PTH proteins, leading to an increase in BMP4 and mammary tissue growth.

Question 14

What is lactogenesis?

Answer 14

Onset of milk secretion

2nd half of pregnancy
- capacity of breast increases to secrete milk
-2-3 day post partum the onset of milk secretion occurs. This happens with rapid increase in milk volume from 36-96 hours from birth

Question 15

What is galactopoiesis?

Answer 15

The maintenance of milk production

When milk is not remove, capillary blood flow decreases and lactation is inhibited. As long as milk is removed the alveoli continues to secrete

Question 16

What is the milk ejection reflex?

Answer 16

New borns suckling stimulates the paraventricular and supraoptic nuclei in the hypothalamus.

This releases oxytocin from the posterior pituitary and contracts the alveoli

Also stimulated by crying or grooming.

Question 17

What is involution?

Answer 17

The termination of milk secretion and gland regression.

Large animals - differentiate during dry period and become non-secretory within 7 days of drying off, aged cells are lost via apoptosis and replced by the division of remaining cells

Rodents - defoliation, epithelial cells fall off and require extensive regeneration.