The Need for Extra Protection and Support

• Integumentary system


  A complex biological system that serves as the outer covering of organisms, providing protection from external environmental factors such as pathogens, physical damage, and dehydration
• Integument


  • An outer covering that protects an animal's body
  • Its main function is to cover and protect the organism
• Among the human body, the skin is the largest organ
• Skin


  • The largest organ of the body
  • Makes up 15% of your total body weight
  • Has a surface area of 1.4 to 1.9 square meters
  • An average person's skin weighs about 3 kg more than twice as much as the brain

  
• Functions of the skin

  • Critical for maintaining homeostasis
  • Provides the first line of defense against diseases
  • Protects your internal structures and organs from being damaged
  • Prevents loss of moisture
  • Protects underlying tissues from harmful effects of the sun
  • Acts as a sensory organ (touch, detects temperature)
  • Helps regulate temperature
  • Produces Vitamin D
• Layers of the skin

  • Epidermis
  • Dermis
  • Subcutaneous tissue or hypodermis

  
• Epidermis


  • The outermost layer, is about as thick as a sheet of paper over most parts of the body
  • It is made up of several layers of epithelial cells
  • The cells of the epidermis are continuously damaged by the environment. Your body deals with this damage not by repairing the cells, but by replacing them by a layer of actively dividing cells at the base of the epidermis called the Keratinocytes

  
• Keratinocytes


  • Cells that make Keratin
  • Keratin is a protein that makes the skin tough and waterproof by preventing fluids and certain substances from passing through the skin
  • Keratinocytes are produced at the bottom layer of the epidermis and they get pushed upward to the top, superficial layer of the epidermis where they are considered cornified. Cornified cells are hardened, flattened, and tough (dead) they've lost their organelles and are just full of keratin
• Melanocyte


  • Cells that produce melanin, which is a substance that gives the skin its color
  • Melanin is actually a pigment that ranges in color from yellow to reddish brown to black
• Langerhans cells


  Langerhans cells prevent things from getting into your skin
• Dermis


  • The middle layer, is between 15 and 40 times thick as the epidermis
  • The dermis is the functional layer of the skin that lies just beneath the epidermis. It is also known as the "true skin"
  • Connective tissues in the dermis make the skin tough and elastic
  • The dermis contains nerve cells, blood vessels, hair follicles, and specialized skin cells
  • Sensations of touch, temperature, and pain originate in nerve cells within the dermis

  
• Thermoregulation


  This allows the body to maintain its right temperature to perform all bodily functions efficiently
• Subcutaneous tissue / hypodermis


  • The innermost layer, varies greatly in thickness among individuals. But in all people, the subcutaneous tissue is much thicker than the epidermis and dermis
  • Subcutaneous tissue, located beneath the skin just under the dermis, is a layer of connective tissues made mostly of fat
  • This skin layer acts as a shock absorber, provides additional insulation to help conserve body heat, and stores energy

  
• Modifications of the skin

  • Hair
  • Nails
  • Glands
• Hair


  • Your hair is made of a protein called keratin
  • Each hair in your body consists of two separate structures, which are the root and the shaft
  • The root part of the hair is found in the epidermis of the skin
  • A follicle, a pouch-like structure, surrounds the root of the hair
  • The hair shaft is made up of dead, hard protein, called keratin in three layers – the cuticle, medulla, and cortex

  
• Nails


  • Nail Matrix - located under the cuticle at the base of the nail, produces new nail cells that form the nail plate
  • Nail Plate - is the hard, translucent keratin layer that protects the tips of the fingers and toes
  • Nail Bed - is the skin beneath the nail plate that provides nutrients and support for nail growth. The nail bed gives the nail its pinkish color due to the blood flow beneath
• Glands


  • Sebaceous glands
  • Sweat glands
• Sebaceous glands


  Sebaceous glands are an organ in your skin that make and secrete sebum. Sebum is a substance that provides a protective coating for your skin to help it retain moisture. Most of your sebaceous glands connect to your hair follicles
• Sweat glands


  These are the glands that secrete sweat through your skin. There are two types of sweat glands: eccrine glands and apocrine glands
• Dermal tissue


  Refers to the plant epidermis, the outer layer of tissue that surrounds the primary body of vascular plants. This includes the roots, stems, leaves, flowers, fruits, and seeds. It is analogous to animal skin

  
• Functions of dermal tissues in plants

  • Above the ground (stems, leaves): Help prevent the plant from drying out by reducing water loss through evaporation. The epidermis secretes a waxy layer called the cuticle, which waterproofs the plant and minimizes water loss.
  • Below the ground (roots): Play a crucial role in absorbing water and nutrients from the soil. The epidermis forms root hairs, which can number up to 40,000 per square centimeter, significantly increasing absorption.
• Epidermis in non-woody plants

  In a young seedling, the dermal tissue of young plants and mature nonwoody plants forms a covering called epidermis. The word epidermis comes from the Greek words epi meaning "upon," and derma meaning "skin." The epidermis acts as the skin's outer protective covering

  
• Periderm in woody plants

  • In trees and woody shrubs, the epidermis is replaced by periderm, the outer areas of the bark
  • Periderm includes cork, which consists of several layers of dead cells
  • Cork cells contain a waterproof chemical and are not covered by a waxy cuticle
  • It contain a waxy, waterproof substance called suberin. Suberin protects the plant from losing water and prevents gases from passing in and out
  • Gases enter and leave the tree or shrub through lenticels, which are round or oval blisters in the surface of the bark
• Layers of bark in woody plants

  • Inner bark - transports sugar from the leaves, store food, and transport it to other parts of the plant (phloem)
  • Outer bark (cork) - Provides protective covering for the plant. Shields stem, roots, and branches from injury, insects, disease, and water loss
• The integumentary system provides essential protection and support for animals, plants, and humans
• It forms a barrier against harmful substances, pathogens, and environmental hazards
• Without the integumentary system and its protective functions, there would be increased risk of infections, dehydration, and physical damage, impacting the overall health and survival of organisms