Histology- Lecture 1

Microanatomy in histology

Includes:

-cells and tissues

-visualize normal and pathological micro-anatomy

-nucleus to membrane to tissue

What creates physiology and pathophysiology?

Cellular shape affects function, which creates physiological or pathophysiology

What are cells?

Cells are life

They are like a tiny animal but don’t have:

• a mouth to eat or drink

• a nose or lungs to breathe

• a urinary system or defection system to get rid of water or waste

• sweat glands to control temp or get rid of other waste products

yet, like whole humans, they eat, drink, breathe, urinate, but how do they do this?

What can we see with a ight microscope?

a typical human cell

What can you see with an electron microscope?

mitochondria, lysosome, ribosome, plasma membrane

What can you see with a scanning tunneling microscope?

protein molecule and hydrogen atom

What do cells mostly consist of?

cells are mostly water -70%

-They live in the water of our body, like fish, which swim and breath in water (an aqueous enviornment)

Explain the composition of cell’s outer surfaces and what their job is

They have a specialized “cell skin” membrane

They control movement of water and molecules in/out

And layers or sheets of cells have the same function (to control water/molecule

movement), just in a larger special physical format, creating body compartments

How to medications get into the cell?

Drugs-bloodstream-travel through blood (many can’t)-messenger sits within cell to interact

Where medications go depends on the “skin” of the membrane

The chemistry of the plasma membrane impacts what?

Impacts the movement of fluids and drugs

What are human cell membranes made out of?

Mostly lipids

What are lipid molecules made out of and how are they linked

Lipids are molecules composed predominantly (but not exclusively) of hydrogen and carbon atoms.

These atoms are linked by nonpolar covalent bonds. Thus, lipids are nonpolar and have a very low solubility in water.

Lipids can be divided into four subclasses:

– fatty acids

– Triglycerides

– Phospholipids

– steroids

nonpolar covalent bonds

• no polarity (electrical potential)

• The bonds don’t interact with H2)

Examples of lipids

Black and tan, and water and oil

Explain fatty acid chain and glycerol on molecules

Fatty acid chains and triglycerides are not soluble in water bc of the C-H methyl groups.

Triglycerides is made up of three fatty acids and a glycerol

Explain phospholipids

Full name is Phosphatidylcholine

Phospholipids are soluble in water and fats because one fatty acid on triglyceride is replaced with a phosphate group. It is electrically charged and thus can interact with water

They are amphipathic molecules that form the cell membrane

Amphipathic molecules

Phospholipids. They have a nonpolar tail (insoluble) and and polar head (soluble) They arrange themselves spontaneously in a circle with the hydrophilic at the outer surface and the hydrophobic in the center

Describe the phospholipid bilayer

Transmembranes-extend through both sides

Phospholipids- make up the bilayer

Cholesterol- add structure. Only found in mammalian cells for structure (For plant, they have a cell wall, hence don’t have cholesterol)

Peripheral proteins- proteins that sit only on one side

Carbohydrate portion of glycoproteins

Integral proteins-permanent

Proteoglycan molecule

Carbohydrate plus core protein

How is the ECM formed in cells

The ECM sits just outside cell. Cells make their own ECM and may make their own

connective tissue

What is part of the ECm that allows cells to form layers?

Specialized junctions (part of ECM) between cells allows cells to join up to form layers…like lining a blood vessel which controls movement, between in and out of blood

Desmosomes

Junctions that hold two cells together; consist of plasma membranes of adjacent cells linked by fibers, yet separated by a 20 nm extracellular space filled with a cementing substance.

Tight Junctions

Cell junction in which extracellular surfaces of the plasma membrane of two adjacent cells are joined together; extends around epithelial cell and restricts molecule diffusion through space between cells.

Unlike the desmosome, which is limited to a disk-shaped area of the membrane, the tight junction occurs in a band around the entire circumference of the cell

Gap Junction

Physical linkages connecting the cytosol between two cells. Molecules can move directly from one cell to an adjacent cell through gap junctions without entering the extracellular fluid

HeLa cells

• In 1951, a young mother of five named Henrietta Lacks visited The Johns Hopkins Hospital complaining of vaginal bleeding

• A biopsy was taken, as was standard for diagnosis and some cells saved for research

• These became the first ever human cells to survive long-term outside the body!

• Some of the most common cells used in research

• Helped develop

– Covid vaccine!

Cell shape is maintained by what?

Cytoskeleton

Cytoskeleton

- network of filaments & tubules made of protein

- give the cell shape and allows the cell to change shape

- helps to locate organelles within cytoplasm

- guides or directs cytoplasmic transport

- provides apparatus for mobility & contractility

Mitochondria

- “Power House” of the cell

- Transforms chemical energy into an energy form the cell can use: ATP

- Uses O2 and produces CO2

- Has its own DNA & ability to replicate itself

- Present in all cell types except red blood cells More numerous in cells that utilize large amounts of energy – i.e. striated muscle cells

Smooth Endoplasmic Reticulum (SER)

Smooth Endoplasmic Reticulum (SER)

Series of tubules

• Walls have no ribosomes so they appear to be smooth

• Involved in lipid synthesis & metabolism

• Involved in synthesis & secretion of steroid hormones

• Involved in membrane formation & recycling

• Hepatic (Liver) form

- detoxifies

- processing some drugs

Sarcoplasmic Reticulum

specialized form found in skeletal and cardiac muscle cells; regulate Ca+2

Rough Endoplasmic Reticulum (RER)

Series of interconnected chambers Walls covered with ribosomes (units of rRNA)

Essential for protein synthesis:

**Highly developed in protein synthetic cells like Fibroblasts

Golgi Complex

Looks like a stack of pancakes

Well developed in secretory cells

Serves as an intermediary between endoplasmic reticulum and the cell

• Processes newly formed proteins

• Concentrates, packages, & marks proteins for intra- or extra- cellular use

• Site of activating “pro-protein”

Endoplasmic Reticulum - Golgi Complex - Secretion

Forming Face- Cis Face. Sequence of cisternae containing compartmentalized enzymes

Maturing face- Trans face