Biology 115 Lecture 3:
Human Organization

T. Irving 01/07/97; revised A.Howard 01/25/00

Epithelial Tissue

cell membrane barrier cell interior and exterior

epithelium is a barrier organ interor vs exterior

protect, retain moisture

needs special mechanisms to transfer nutrient and wastes out across epithelium

squamous epithelium

cuboidal epithelium

columnar epithelium

simple or stratified

epithlial tissue is connected to underlying connective tissue by way of basal lamina or basement membrane

Certain epithelial cells are specialized for secretion

glands eg. goblet cells secrete mucus in digestive tract

or multicellular

exocrine glands empty via ducts to some other organ

endocrine glands empty directly to the blood stream

Epithelial cells have specializations of their plasma membranes

• Tight junctions: make cells impermeable
• Desmosomes (cell to cell spot welds)
• Hemi-desmososmes (cell to "basal lamina" spot welds)
• Adhesion junctions (belt desmosomes):
  mechanical junctions, connects cytoskeleton
• Gap junctions (communication junctions)

Connective Tissue

Consists of cells & matrix

The connective tissue matrix is secreted by the cells in the connective tissue,except in the case of blood

5 major types:

• Loose connective tissue
  fibroblasts (cellular) suspended in jelly like matrix composed of white collagen and yellow elastin
  generally functions to bind organs together
• Adipose tissue
  fibroblasts specialized for storing fat & insulation
• Fibrous connective tissue:
  Tendons and Ligaments
  mainly straps of tightly packed collagen fibers
  tendons muscle-bone, ligaments bone - bone
• Cartilage
  Cells are embedded in lacunae in a solid, flexible matrix
  • Hyaline cartilage found in nose, ends of long bones, ribs
    Entire skeleton starts off as Hyaline cartilage, gradually ossifies to bone
  • Elastic cartilage
    contains more elastin - found in outer ear
  • Fibrocartilage
    strong collagen fibers, found in between vertebrae, knee joints
• Bone
  • Compact bone
    rigid - hard matrix - lots of Calcium
  • Spongy bone
    ends of long bones; many spaces between bony bars and plates
• Blood
  • Plasma 92% water, 8% soluble materials
  • Red blood cells (erythrocytes) carry oxygen
  • White blood (leukocytes) cells aid in fighting infection
  • Platelets

Muscular tissue

3 main types:

• Skeletal
  connect via tendons to bones
  voluntary, fast, striated;
  contains multinucleated long fibers
• Smooth (visceral)
  no striations; not under voluntary control
  line viscera i.e intestines, stomach, uterus, blood vessels etc.
  contract more slowly than skeletal muscle
  In many cases move things along by process of peristalsis
• Cardiac
  Striated like skeletal
  1 nucleus/cell; branched and fused
  joined by intercalated disks (desmosomes & gap junctions)
  fast electrical communication throughout the tissue
  slow strong contractions

Nervous Tissue

Brain & spinal cord contain cells called neurons

cell body dendrites and axons

Nerves consist of long dendrites and/or axons bundled with connective tissue

Nerves conduct impulses from sense organs to the spinal cord and to the brain

Motor impulses travel from the brain trhough the spinal cord to the muscles

Neuroglial cells support and provide nutrients to the neurons

Skin

Skin contains receptors

Specialised nerve endings for

pain, touch, temperature, pressure

concentrated particular parts of the body eg. fingers

Epidermis is the outer layer of skin consisting of living and keratinised squamous epithelial cells

Dermis is the layer below consisting of fibrous connective tissue. Contains hair follicle sebaceous glands and sweat glands , receptors, blood vessels and nerves

Organ Systems

Homeostasis

Organ systems are organized to maintain internal environment within very narrow limits regardless of what goes on outside

• osmoregulation ~ 0.9% NaCl
• thermoregulation ~ 37°C
• pH ~7.4
• Blood pressure ~120/80 systole/diastole

Mechanisms:

Blood constantly circulates adding oxygen, removing nutrients

& removing CO₂ water, waste products

Hair follicles in skin have muscles that make hairs stand up or lie flat. Trapped air helps retain heat.

Squamous epithelium generally separates blood and tissue fluids internal vs external environment

Digestive system by processing food keeps a steady supply of ATP, fatty acids and amino acids

This also controls pH

All examples of a negative feedback control system

If something gets too high, something operates to bring it back down

If something gets too low, other mechanisms act to raise its levels.

Main function of the endocrine system