Study Question Three

• Q3. What are the primary tissue layers, and what primary tissue types do they contribute to?
• The primary tissue layers are

  • ectoderm
  • endoderm
  • mesoderm
• Ectoderm forms the epithelial tissues of the skin and nervous tissue which include the brain and spinal cord
• Mesoderm gives rise to muscle tissue, connective tissue (like blood and bones), and epithelial tissue of kidney and reproductive organs
• Endoderm develops into the epithelial tissue of internal organs such as the digestive and respiratory tracts
• Ectoderm consists of two subtypes:

  • Epithelial tissue
  • Nervous tissue
• Mesoderm consists of three subtypes:

  • Connective tissue proper
  • Fluid connective tissue
  • Supporting connective tissue
• Mesoderm with the connective tissue proper consists of two subtypes:

  • Loose connective
  • Dense connective tissue
• Endoderm consists of one subtype:

  • Epithelial tissue
• Ectoderm with the epithelial tissue forms the outer layer of the skin (epidermis) and lines various organs
• Ectoderm with the nervous tissue develops into the brain, spinal cord, and peripheral nerves
• Mesoderm with the connective tissue proper with loose connective tissue such as areolar, adipose, and reticular tissues
• Mesoderm with the connective tissue proper with dense connective tissue such as dense regular, dense irregular, and elastic tissues
• Mesoderm with the fluid connective tissue includes blood and lymph
• Mesoderm with the supporting connective tissue includes cartilage (hyaline, elastic, and fibrocartilage) and bone
• Endoderm with the epithelial tissue forms the lining of internal organs such as the digestive and respiratory tracts
• Loose connective tissue has fibers which create loose open framework

  • areolar tissue
  • adipose tissue
  • reticular tissue
• Dense connective tissue has fibers which are densely packed

  • dense regular
  • dense irregular
  • elastic
• Blood is contained in cardiovascular system
• Lymph is contained in lymphatic system
• Cartilage is solid and rubbery matrix

  • hyaline cartilage
  • elastic cartilage
  • fibrous cartilage
• Bone is solid, crystalline matrix
• Connective Tissue Proper has the types of loose and dense
• Fluid Connective Tissue has the types of blood and lymph
• Supporting Connective Tissue has the types of cartilage and bone
• Areolar Tissue locations:

  • within and deep to the dermis of the skin and covered by the epithelial lining of the digestive, respiratory, and urinary tracts
  • between muscles
  • around blood vessels, nerves, and joints
• Areolar Tissue functions:

  • cushions organs
  • provides support but permits independent movement
  • phagocytic cells provide defense against pathogens
• Adipose Tissue locations:

  • deep to the skin, especially at sides, buttocks, and breasts
  • padding around eyes and kidneys
• Adipose Tissue functions:

  • provides padding and cushions shocks
  • insulates (reduces heat loss)
  • stores energy
• Reticular Tissue locations:

  • liver
  • kidney
  • spleen
  • lymph nodes
  • bone marrow
• Reticular Tissue functions:

  • provides supporting framework
• Dense Regular Connective Tissue locations:

  • between skeletal muscles and skeleton (tendons and aponeuroses)
  • between bones or stabilizing positions of internal organs (ligaments)
  • covering skeletal muscles
  • deep fasciae
• Dense Regular Connective Tissue functions:

  • provides firm attachment
  • conducts pull of muscles
  • reduces friction between muscles
  • stabilizes relative positions of bones
• Elastic Tissue locations:

  • between vertebrae of spinal column
  • ligaments supporting penis
  • ligaments supporting transitional epithelia
  • in blood vessel walls
• Elastic Tissue functions:

  • stabilizes positions of vertebrae and penis
  • cushions shocks
  • permits expansion and contraction of organs
• Dense Irregular Connective Tissue locations:

  • capsules of visceral organs
  • periostea and perichondria
  • nerve and muscle sheaths
  • dermis
• Dense Irregular Connective Tissue functions:

  • provides strength to resist forces applied from many directions
  • helps prevent overexpansion of organs, such as the urinary bladder
• Red Blood Cells also known as erythrocytes, are responsible for transport of oxygen in blood

  Red blood cells account for about half the volume of whole blood and give blood its color
• White Blood Cells also known as leukocytes, defend the body from infection and disease
• White Blood Cells have Monocytes which are phagocytes similar to the free macrophages in other tissues