Test 2 A&p

• A group of cells with a common embryonic origin that function together to carry out specialized activities
  
• They include various types, ranging from hard (bone) to semisolid (fat) to liquid (blood).
  

• The study of the microscopic anatomy of cells and tissues - it is a branch of pathology.
  
• ~37-100 trillion cells comprise the human body, and there are over 200 different types
  

• No single cell type is said to be the "typical" cell of the human body.
  
• Each cell type has features particular to its function.
  

• Many tissues are formed by grouping cells together using a variety of intercellular junctions.
  
• - 3 major types in humans
  

1. Anchoring junctions -- adherins, desmosomes, hemidesmosomes

2. Communication junctions -- gap junctions

3. Occluding -- tight junctions

Make an adhesion belt (like the belt on your pants) that keeps tissues from separating as they stretch and contract.

-- Cadherin is a glycoprotein that forms the belt-like "plaque".

• Act as "spot welds" between cells
  
• They also use cadherin glycoprotein (plus intermediate filaments) to hook into cytoplasm.
  
• Common skin and muscle
  

Half-welds that join cells to a basement membrane.

Pores (connexons) that allow small substances to pass between cells.

Ions can pass between cells using these

common in cardiac muscle and smooth muscle tissue

If one of the cells gets sick or dies, these seal like a safety hatch to prevent damage to other cells.

• Found in tissues where a leak-proof seal is needed between adjacent cells
  
• Very important in organs like the stomach and bladder
  

Why?

All of the different types of cells in the body are classified under one of the 4 basic tissue types:

1. Epithelial tissues
2. Connective tissues
3. Muscular tissues
4. Nervous tissues

• Covers body surfaces, forms glands, and lines hollow organs, body cavities and ducts.
  

Functions in protection, absorption, filtration, excretion, secretion, and sensory reception.

• Characteristics
  

Supported by connective tissues, avascular but innervated, can typically regenerate.

• Function in protection, support, and binding of organs.
  
• fat (adipose) is a type of C.T. that stores energy
  
• Red blood cells, white blood cells, and platelets are part of the C.T. of blood
  

generates the physical force needed to make body structures, or substances, move. They also generate heat that can be used by the body.

used for internal communication, to detect changes in the body, and provide for quick response to stimuli.

internal communications

Brain

spinal cord

nerves

Contracts to cause movement

Muscles attached to bone (skeletal)

muscles of the heart (cardiac)

muscles of walls of hollow organs (smooth)

forms boundaries between different environments, protects, secretes, absorbs, filters

Lining of digestive tract organs and other hollow organs.

Skin surface (epidermis)

Supports protects, binds other tissues together

Bones

Tendones

Fat and other soft padding tissue

Endoderm, Mesoderm, and Ectoderm

-- Epithelial tissues are derived from all three germ layers

-- C.T. and muscle are derived from mesoderm

-- Nervous tissue develops from ectoderm

• Epithelium is used to line surfaces and form protective barriers. It is also used in secreting things like mucous, hormones, and other substances.
  
• Epithelial have a;
  

-- Free apical surface

Facing the body surface, cavity, or lumen (interior space)

-- Basal surface

Typically attached to underlying basement membrane

-- Lateral surface

can contain cell junctions

• The basal (bottom) layer of the epithelium secretes a basal lamina
  
• The underlying C.T. secretes a reticular lamina.
  

Together, the basal lamina and the reticular lamina form an extracellular basement membrane on which the epithelium sits

• Named according to the shape of their cells, and the thickness or arrangement of their layer (of cells).
  
• If different shapes are present in layers of cells, the epithelium is always named by the shape of cells in the apical (outermost) layer.
  

Flat, wide; paving stone like shape

Cells as tall as they are wide; a cube shape

Cells taller than they are wide; a rectangular like shape

One layer. All cells in contact with basement membrane

Appears to have layers, but in reality all cells go from the apex to the base

Two or more layers. Only basal layer in contact with basement membrane

Able to change shape (transition) between squamous and cuboidal/columnar.

Forms a single layer of column like cells

Functions in absorption and secretion

± cilia, ± microvilli, ± goblet cells.

• Minute, finger like extensions of plasma membrane
  
• increase surface area for absorption
  

Simple columnar cells that have differentiated to acquire the ability to secrete mucous.

• Appear to have layers due to nuclei which are at various depths.
  
• In reality, all cells are attached to the basement membrane in a dingle layer
  

-- some do not extend to the apical surface

• Functions in absorption and secretion
  
• May contain mucus-secreting cells and bear cilia.
  

• Has an apical surface made up of two or more layer of cube-shaped cells
  
• Very rare
  

-- location include sweat, mammary, and salivary glands

Very rare but does exist in some tissue

• Ocular conjunctiva of the eye
• Pharynx
• Uterus
• Salivary Glands

• Able to change shape depending on the state of stretch in the tissue.
  

-- Allows organs like the bladder to stretch to a larger size and then recoil back to a smaller size.

• The apical "dome cells" of the top layer (seen here in relaxation) are identifiable feature and signify an empty bladder.
  
• In a full bladder, the cells are flattened.
  

Certain ones are associated with specific body locations.

-- Stratified squamous epithelium is a prominent feature of the outer layers of the skin.

comprises epithelial membranes and lines the blood vessels.

is common in the digestive tract

is a characteristic of the upper respiratory tract.

is found in the bladder

lines ducts and sweat glands