1. Parenchyma– Contains duct system and secretory unitsIn resting gland there is no secretory units– Duct system consists of:4.Intralobular ducts: in the lobules ,lined with 2 layers of cubical cells5.Lactiferous ducts: results from union of intralobular ducts, dilated to form lactiferous sinuses , their proximal parts lined with st.col .Epith.6.Lactiferous sinuses and terminal parts are lined with st. sq. epith.
During puberty• Their development forms one of the 2ry sex characters• Increase in vol. of ducts with cell proliferation• accumulation of adipose tissue in the inter lobar and interlobular C.T.• All these changes are due to in ovarian hormones with minimal appearance of alveoli at time of ovulation where estrogen reaches peak there is in adipocytes lipid acc.and breast in size
During pregnancy• The glands undergo intense growth due to proliferation of ducts + production of secretory tubules and alveoli• The C.T. stroma and adipose tissue decrease• No visible signs of secretion except in late pregnancy
Secretory alveoli• Begin to appear at the 6th month of pregnancy• They are lined with columnar epith.• They are surrounded by myoepithelial cells• They contain colostrum in late months of• Pregnancy ***Their mode of secretion is apocrine• Mode of secretion.
Hormones controlling breast enlargement 1-Ovarian hormones :Estrogen increases during pregnancy acting on duct system 2-Progestrone by (corpus luteum ) 2- placental hormons act on secretory alveoli• Placental Hormones are :progestrone ,placental mammotrophins 3-Anterior pituitary: growth h &prolactin h. 4-Suprarenal: glucocorticoids.
Lactating mammary gland• Consists of compound tubulo-alveolar• gland 1.Stroma is thin 2.Parenchyma is formed of duct system and alveoli 3.Alveoli are lined by columnar or cubical epith. Filled with vacuolated milk secretion 4.Milk secretion is controlled by 5.Prolactin which stimulate alveolar cells secretion 6.Oxytocin: contraction of myo-epithelial Cells ,squeezes alveoli cause milk ejection
In lactation• Milk acc. In the lumen of secretory part and ducts• Cells. Milk containing lipid vacuoles and also protein vacuoles• Milk composition : 1. Lipid 4% 2. Protein 1.5% 3. Lactose 7%• Colostrum : it contains less fat and more proteins and rich in antibodies (IgA)
Histological structure of the skin• Formed of two layers:• 1- Epidermis• 2- Dermis
Types:1-THICK SKIN• EPIDERMIS: IS THICK:0.8mm in palm ,1.4 mm in sole.• Contains 4 types of cells:• 1-keratinocytes (85% of cells)• 2-Melanocytes• 3-Langerhans cells• 4-Merkel cells• ِArranged in five layers.
Layers of epidermis are • Stratum basale (germinativum) • Stratum spinosum • Stratum granulosum • Stratum lucidum (may not be present) • Stratum corneum
SWEAT GLANDS• Merocrine glands: • Apocrine glands:• Allover the body • Axilla,groin,pubic region• Secretory cells 2types • Secretory part similar• Clear cells cubical rich • To mero. With in glycogen granules. • Wider lumen• Dark with narrow basal part • Their ducts are lined with •• Apical glycoprotein granules With 2 layers of cubical cells but open into hair follicles• Myoepithelialt cells • Secretion stim.by sex• Ducts lined by 2layers of cubical cells • hormones
sweat glands Two types of sweat glands – Eccrine • Not associated with hair follicle • Duct segment – less coiled, leads to epidermis – Stratified cuboidal epithelium • Secretory segment – in deep dermis or hypodermis – Secretory cells – Myoepithelial cells lie between secretory cells, contraction expels sweat – Apocrine • Found in limited areas • Empty into hair follicle
Structures of skin: hair follicle • Invagination of epidermis • Hair contains keratin and melanin • Dermal papilla – Connective tissue invagination into bulb, has capillary network • Matrix – Germinative layer adjacent to dermal papilla – Also contains melanocytes • Sebaceous gland – Secretion empties into hair follicle • Arrector pili muscle – Smooth muscle, inserts on hair follicle and base of epidermis(dermal papilla) bulb
The hair is formed of• Shaft: medulla, cortex and cuticle• The hair follicle is formed of :• Inner root sheath formed of:• Cuticle ,Huxleys layer,Henles layer• Outer root sheath: identical with Malpighian• Layer of epidermis• Connective tissue sheath.