BIOL-400Follicle Development
The wool-producing ‘factory’ is the 50 million or so follicles embedded in the skin of sheep. This unit covers in detail, how these follicles form, what cellular and molecular processes produce the fibre, how genetics and nutrition affect these processes, and how genetic engineering might be used to produce a better fibre. With an understanding of the biology of the skin and the fleece, the characteristics of the wool follicle and fibre can be related to production, technology and the processing of wool.
The lifetime characteristics of wool production are determined by the extent and pattern of follicle initiation in the fetal animal. This theme examines those factors determining follicle development in skin.

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BIOL-400-100Genotype and Follicle Development
Genotype clearly governs many of the follicle characteristics such as density, S:P ratio, follicle size and follicle shape etc
BIOL-400-100-100Follicle initiation and genotype
The development of wool follicles has been described in detail for the Merino and it is well established that no new follicles are initiated after birth. The initiation and development of hair follicles is a complex process involving interactions between the fetal epidermis, specialised populations of dermal cells and developmentally regulated cytokines. This module summarises the results from a paper that describes differences and similarities between sheep of different genotypes in their pattern of follicle initiation and development. This study was undertaken to examine the pattern and timing of wool follicle development in the New Zealand Romney, Merino and Merino x Romney (MxR), Drysdale and Wiltshire sheep during fetal and early post-natal life in order to determine the period or periods during which genotypic differences in follicle density occur.
BIOL-400-200Follicle Initiation and Development
The formation of a follicle from epidermal and dermal cells is a response to complex cell signalling events. This topic examines the mechanisms whereby follicles are initiated in fetal skin.
BIOL-400-200-050Follicle initiation and development
This module describes follicle initiation and development of both primary and secondary follicles. Diagrams and photomicrographs are used to describe the changes that occur in follicle development, density and S:P ratio.
BIOL-400-200-100Wool follicle initiation: regulation of diameter and density
This module brings together follicle initiation and wool production.
BIOL-400-200-150Formation of appendages
To understand the formation, initiation and development of follicles it is useful to study other organs that develop in a similar way. Epithelial-mesenchymal interactions are essential for follicle initiation and a number of molecules have been implicated in follicle initiation and development. This module will revisit follicle morphogenesis by outlining mouse hair development and compare it to the the development of feathers and vertebrate limbs at the molecular level. The module also addresses the question whether these developmental systems can be used as a working model for developing an hypothesis for the initiation and development of the wool follicle in sheep.
BIOL-400-200-200Models of follicle initiation derived from morphological observations
There are a number of mechanisms and processes that cause cells to behave differently to their neighbours. Experiments to examine the mechanism responsible for follicle initiation and fibre formation include morphological observations, epidermal/dermal recombinations, chemical modifications, mechanical modifications, genetic modifications and changes in gene expression patterns. By taking these results into account, models/theories can be developed to explain follicle initiation and fibre formation. One of these, the reaction-diffusion theory, has been used to explain wool follicle initiation and fibre formation. This module describes the morphological observations that provide clues to the nature of the mechanisms controlling follicle initiation.
BIOL-400-300Follicle Initiation and Nutrition
While genotype is the main determinant of follicle development, maternal nutrition can play an important role thereby influencing lifetime wool quantity and quality.
BIOL-400-300-050Follicle initiation and nutrition
The development of wool follicles has been described in detail for the Merino and it is well established that no new follicles are initiated after birth. The initiation and development of hair follicles is a complex process involving interactions between the fetal epidermis, specialised populations of dermal cells and developmentally regulated cytokines. This module summarises the results from a number of papers that describe the effects of prenatal ewe nutrition on follicle initiation and development.
BIOL-400-300-100Follicle initiation, wool growth and maternal nutrition
This module summarises the results from experiments that describe the effect of prenatal nutrition on the wool production of lambs.
BIOL-400-400The Influence of Hormones and Growth Factors on Follicle Development
Hormones and growth factors influence follicle development in utero. The effects of hormones and growth factors are examined in detail in this section.
BIOL-400-400-050Molecules involved in follicle initiation
This module lists the possible mechanisms and the molecules that have been implicated in follicle initiation and development. A table of some molecules involved in follicle development is included.
BIOL-400-400-100Epithelial-mesenchymal interactions in the developing follicle
Epithelial-mesenchymal interactions are essential for follicle initiation and a number of molecules have been implicated in follicle initiation and development. This module examines the role of the epithelium and mesenchyme in skin appendage formation.
BIOL-400-400-150Effect of cortisol on follicle initiation
The development of wool follicles has been described in detail for the Merino and it is well established that no new follicles are initiated after birth. The initiation and development of hair follicles is a complex process involving interactions between the fetal epidermis, specialised populations of dermal cells and developmentally regulated cytokines. This module describes an experiment that examined the effect of a cortisol analogue on follicle initiation and development.
BIOL-400-400-250Follicle initiation, EGF and FGF-2
The initiation and development of hair follicles is a complex process involving interactions between the fetal epidermis, specialised populations of dermal cells and developmentally regulated cytokines. This module summarises the effects of two growth factors, EGF (epidermal growth factor) and FGF-2 (Fibroblast growth factor – 2) on follicle initiation and development.
BIOL-400-400-275Follicle initiation and thyroid hormones
This module summarises the effects of thyroid hormones on follicle initiation and development. A diagram illustrates the changes that occur when fetal lambs are thyroidectomised.
BIOL-400-400-300The Reaction Diffusion system can describe follicle initiation
There are a number of mechanisms and processes that cause cells to behave differently to their neighbours. Experiments to examine the mechanism responsible for follicle initiation and fibre formation include morphological observations, epidermal/dermal recombinations, chemical modifications, mechanical modifications, genetic modifications and changes in gene expression patterns. By taking these results into account, models/theories can be developed to explain follicle initiation and fibre formation. One of these, the reaction-diffusion theory, has been used to explain wool follicle initiation and fibre formation. This module describes how the reaction diffusion (RD) system can explain follicle initiation.