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Lecture 6

Lecture 6.docx

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Jennifer Harris

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Lecture 6: BIO230H1 Pg. 1419-1423 Epidermal Cells Form a Multilayered Water Barrier  Interfollicular epidermis is multilayered epithelium composed of keratinocytes  The cells change their appearance  There are basal cells are several layers of prickle cells  Granular layer barrier to the movement of water and solutes  The outer cells are squames filled with keratin Differentiating Epidermal Cells Express a Sequence of different Genes as They Mature  Basal cells are moving and dividing  Kertinocyte in the basal layer is transformed  Terminal cell differentiation: process in precursor cell acquires its final specialized characteristics and usually permanently stops dividing Stem cells in the Basal Layer Provide for Renewal of the Epidermis  Humans renew the cells in the basal side  The stem cells: differentiate cells  Defining properties of a stem cell  1. It is not itself differentiated  2. It can divide without limit  3. When cell divides it can retain a stem cell to commit it to terminal differentiation  Stem cells can divide into many different tissues The Two Daughters of a Stem cell do not always have to become different  Environmental asymmetry and divisional asymmetry  Division of a stem cell could generate two initially similar daughter cells with two daughter cells  There is a renewal patch that can occur if the epidermis is damaged  Observations can be used to maintain of stem cell characteristics The Basal Layer Contains Both Stem Cells and Transit Amplifying Cells  Basal cells are terminally differentiated cells  Used for amplifying cells: in transit from a stem cell character to a different characteristics Pg.1430-1433 Auditory Hair Cells have to Last a Lifetime  Auditory hair cells: held rigid framework of the supporting cells  Supporting cells that laid the extracellular matrix  Stereocilia have vibrated to create different ion channels  The auditory hairs last a lifetime  If they are destroyed they cannot be regenerated  Partial treatment can occur by using a virsus that is engineered to have a copy of Atoh1 gene Most Permanent cell Renew Their Parts: the Photoreceptor Cells of the Retina  Neutral retina are complex if the sensory epithelia  Consists of many layers and mass pass through cells called photoreceptors  Photoreceptor: classified as rods or cones buried in the pigment epithelium  Visual pigments can be sensed by the photoreceptors Pg. 1454-1459 The Production of Each Types of Bloo
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