Tissues – four kinds of tissues: epithelial, nervous, connective, and muscular.
- Tissues are groups of similar cells that perform together to serve a specialized function.
Figure 1. Different types of tissues
Function of epithelial tissue:
1. Physical protection/barrier eg. Skin @ outer layer
a. Acts as selective barrier between environment and internal structures 2. Absorption – regulates the transport of substances into the body eg. Small intestines
3. Sensations – Specialized sensory receptors derived from epithelial tissues eg. Cones and rods of retina, olfactory
in the nose and taste buds
4. Secretion – release of ‘things’ specialized secreting epithelial tissues known as glands
a. Exocrine – secretes to outside via ducts b. Endocrine – secretes hormones into blood stream
Structure of epithelial – sits on top of basement membrane. (Figure 2)
- Thin extracellular layer that separates
epithelial from underlying connective tissues.
- Acts as regulator for movement of
molecules to deeper connective tissues
- Acts to anchor epithelium to underlying
- Blacks chance molecules such as virus.
Figure 2. Structure of Epithelial
Classification of Epithelial tissue
a. Squamous – irregular sides flat, thin
b. Cubodial – thicker and cubes
c. Columnar – Column looking like (long
a. Simple – one single layer
b. Stratified – multiple layers
Types of Epithelium
Simple squamous – digestive tract, absorption
Simple cuboidal – absorption (nephron, kidneys) water absorption is most optimal
a. Non-ciliated – microvilli increases surface area for better absorption and secretion
a. Goblet cells to produce mucin (digestive)
b. Ciliated – hair like projections (goblets present) uterine and respiratory tract
Figure 3a. Non-ciliated microvilli - Epithelial Figure 3b. Ciliated epithelium
Stratified Squamous – adopted for protection (epidermis of skin)
Stratified cuboidal – protection, lining of ducts and glands (exocrine)
Stratified columnar – deep and plenty of protection, (male uretha and front of eyeball)
Psuedostratified ciliated columnar – Fake layers every cell attached to basement membrane. respiratory system pushes
up and out with mucin.
Transitional epithelium – can flatten/thicken eg bladder when full they thinner and flat. When empty they are thick.
2. Connective tissues
- Connective tissue proper (loose and dense)
- Blood Development of Connective Tissues
Mesenchyme are nonspecific embryological connective tissue.
Functions of connective tissues:
Support – bone forms framework and a place for muscle
- Cartilage forms frame work for structures like
- Connective tissue proper forms capsules for organs
Bind – Ligaments are bone to bone, tendons are muscle to bone
Storage – Fat as connective tissue stores energy (adipose tissue) or bone is storage for calcium and phosphorous.
Transport – Blood transport nutrients, waste and hormones.
Protection – Adipose tissue protect vital organs like the kidneys as do skeletal protects brain, spinal cord, heart and
Immune protections – connective tissue contain WBC to destroy poathogens.
Connective tissue proper – comes divided into two categories:
1. Connective tissue proper loose
2. Connective tissue proper dense
Connective Tissue Proper Loose – Areolar, Adipose, Reticular
1. Areolar – least specialized broad function, holds water around capillaries
a. Found in almost all different type of cells and fibers - Fibroblasts are cells in Areolar tissue that produce protein fibers and ground substance (Viscous fluid, colour-less
solution – tissue filler added extra support and movement of nutrients)
i. Collagen (white) – strong, flexible yet resistant to stretching
ii. Elastic (Yellow) – made of elastin; allow for stretch and recoil