Tissue Development and Wound Healing

Body Defenses Body defense system includes skin mucous membranes, strong acid in stomach, etc. They work to fight off invaders

When Tissue is damaged:  Healing starts almost immediately  Inflammatory Response is triggered  Immune Response is started immediately

Inflammatory Response  Non-Specific body response  Occurs whenever the body is injured (no matter where on the body you are hurt)  Prevents further injury

Immune Response  Very specific body process  Attacks a recognized invader (bacteria, virus, microbes, foreign substance)  Increased Metabolism  Increases Body Temperature

Tissue Repair and Wound Healing  2 methods of tissue repair: 1.) Regeneration 2.) Fibrosis  Healing (structures and time) depends on 2 things: 1.) the type of injury 2.) the severity of the injury

Regeneration  Replacement of destroyed and damaged tissues by the same kind and type of cells  Good blood supply is essential to healing  Cleaner incisions repair better and heal more successfully than jagged lacerations

Fibrosis (scar)  Repair of tissue and a scar is the result  Dense fibrous connective tissue replaces the original tissue

Healing Process  Step 1: Capillaries allow clotting proteins into injured area  Step 2: --Clot is constructed to stop blood loss which holds edges of wound together, and forms barrier (so bacteria can’t seep into surrounding tissue) --When exposed to air the clot dries to form a scab

 Step 3: Granulation Tissue Forms (delicate pink tissue with many capillaries, stemming from nearby intact areas) Granulation Tissue contains: 1.) Phagocytes to get rid of the clot 2.) Connective tissue cells that could produce a scar

 Step 4: Surface epithelium regenerates beneath scab, and then later on the scab falls off *Epidermis, Mucus membranes, Fibrous connective tissue and bone regenerate well *Skeletal muscle regenerates poorly *Cardiac and Nerve Tissue is replaced by scar

Scar Tissue  Scar tissue is strong but less flexible  Scar tissue can’t perform the normal functions of that tissue  Scar tissue in muscles or muscular organs such as the heart or bladder hinder the function of that organ

Development  Life begins as a single cell that divides thousands of times to form specialized tissues  Mitosis continues in almost all cells until the end of puberty (full grown)

Development  After puberty only certain cells routinely divide ex.) skin, intestinal lining  Some cells stop dividing, like liver, but can replace themselves if injured  Heart muscle and nervous tissue cannot replace itself (amitotic)

The Aging Process  thinner epithelium – easily damaged, less elastic  “dry out” – less oil, mucus, sweat  fewer hormones that control metabolism & reproduction  less collagen  bones become porous and weaken  Atrophy (wasting away) of nervous and muscle tissue

Contributions to Aging Causes and Various Possibilities of Aging:  Chemicals? Toxins, drugs, carbon monoxide  Physical factors? X rays, UV light  Genetic clock? Biological Clock?  Poor circulation (decreased nutrients and oxygen to cells) One question for you: Can you prevent aging?