Histology (tissue types)

what are the primary embryonic tissue types?

ectoderm (outer layer), mesoderm (middle layer), endoderm (innermost layer)

ectoderm

• Derivatives kin, eyes, brain

• “attractoderm” - everything that makes you attractive

mesoderm

• Derivatives cardiac (heart), bone, blood 

• “Mesochyme”

endoderm

• Mucus membranes of the GI & respiratory system

• Helps with digestive glands

what are the 4 primary tissue types:

Epithelium, connective, muscle, nervous

what do epithelia tissues do?

Protect, Absorption, filtration, excretion, secretion, sensory

what are epithelial tissues key characteristics

• Apical Surface: borders open space

• Basal surface: next to underlying connective tissue

how to identify epithelial tissues?

• Shape: Squamous (flat), Cuboidal (square shape), Columnar (long columns)

• Number: Simple (1 layer), Stratified (multiple layers)

simple epithelium examples

simple squamous (function & location)

• Easy diffusion; secretion

• Found in lungs, kidneys, vessels

simple cuboidal (function & location)

• Secretion & absorption

• Found in kidneys, glands, ovary

simple columnar (function & location)

• Secretion & absorption

• Found in GI, gall bladder, glands

Pseudostratified Columnar Epithelium (function and location):

• Single, but appears stratified due to different heights

• Secretion, propel mucus

• (cilia) trachea and upper respiratory tract

• (non-cilia) in sperm carrying ducts and large glands

Stratified Squamous Epithelium (function and location) :

• Protection

• (Non keratinized) esophagus, mouth, vagina

• (keratinized) skin

Stratified Cuboidal Epithelium (function and location):

• Secretion

• Sweat glands, ovaries, testes

Transitional Epithelial (urothelium) (function and location):

• Stretches

• Urinary tract & bladder

Connective tissues

• 11 types of connective tissue

• Connective tissue proper =fibrous connective tissue

what does connective tissue do?

• Binding & support, Protection, Insulation, Storing, Transportation

connective tissue characteristics

• Extracellular matrix > cells

• Common Origin

Proper Connective tissues: Loose Areolar

• Support, defense, storage

• Universal; present in all mucous membranes as lamina propria 

Proper Connective tissues: adipose (fat)

• Support, defense, insulation, storage

• Universal; ~18% of weight

• Looks like stone or bubbles

Proper Connective tissues: loose recticular

• Support defense cells

• Lymphoid organs (lymph nodes, bone marrow, spleen)

• Looks like blueberry bush

Proper Connective tissues: dense regular

• Strength

• Tendons, ligaments, aponeuroses

Proper Connective tissues: dense irregular

• Strength (structural and functional)

• Capsules, dermis, digestive tract

• Looks like a steak marbling

Proper Connective tissues: dense elastic

• Recoil

• Arteries, some ligaments, lungs

• Looks like curly hair strands 

Cartilage tissues: hyaline (articular cartilage)

• Support and cushion

• Ends of bones, costal cartilages, nose, trachea, and larynx

• Googly eyes

Cartilage tissues: elastic

• Shape and flexibility

• External ear; epiglottis

• Rubber bands

Cartilage tissues: fibrocartilage

• Strength and shock absorption

• Intervertebral discs, menisci, pubic symphysis

• Feathers

Cartilage tissues: bone

• Hard, calcified matrix (osteons) with peripheral osteocytes (black dots)

• “Tree ring” pattern

• Support and protection

Cartilage tissues: blood

• Non traditional:

• Cells (erythrocytes) surrounded by fluid (plasma)

• Carry nutrients, wastes, respiratory gases, and other substances

Muscle Tissue types

Skeletal muscle, smooth muscle, cardiac

What do muscle tissues do

• Contraction/movement

Voluntary (skeletal) or involuntary (smooth and cardiac)

Skeletal muscle:

• Long, cylindrical shaped with many peripheral nuclei

• Patterned striations

• L: Skeletal muscle

Smooth muscle

• Spindle shaped (thick in the middle, thinner on the end) with one central nucleus

• No visible striations

• L: digestion, urinary tract/bladder, uterus, blood vessels

Cardiac muscle:

• Branching cells with one central nucleus

• Cells connected with intercalated discs (dark bands of tissue (dark pink lines)

• L: heart

Nervous tissues

Responds to a stimuli

• Generates impulse 

Transmit impulse

Nervous Tissue key characteristics:

Cell body, dendrites, single axon

Neurons:

Highly specialized nerve cells

Neuroglia:

Support, insulate, and protect the neurons

Glandular Epithelia:

1. All glands produce a product, or secretion

• Serous (thin, watery) or Mucous (mucin)

• Water-based with protein, lipid, or steroid

2. Classified by where they secrete

• Endocrine (inside) or exocrine (outside)

3. Classified by number of cells

• Unicellular or multicellular

Cutaneous membranes:

• The superficial layer is made up of keratinized stratified epithelium (epidermis) attached to connective tissue (dermis)

• Only dry membrane (exposed to air)

Mucus membranes:

• Made of superficial layer of stratified squamous/simple columnar over a layer of areolar connective tissue (lamina propria)

• Line all body cavities that open to the outside world

- Digestive* 

- Respiratory*

- Urinary 

• Wet membrane 

- Absorption & secretion

Serous membranes:

• Simple squamous (mesothelium) over a thin layer of areolar connective tissue

• Line all body cavities that do NOT open to the outside world

- Pleurae 

- Pericardium 

- Peritoneum 

• Wet membrane

- Secrete serous fluid