Microanatomy

Plasma membrane

The membrane that the cell is bound by, separating the cell from the external environment

Substance of the nuecleus

Nucleoplasm

What is the nucleus bound by

Nuclear envelope

Cytoskeleton

Cytosolic network of minute tubules and filaments

Phospholipid polar head composition

Glycerol conjugated to nitrogenous compound such as choline, ethanolamine, or serine via phosphate bridge

What is ratio of cholesterol to phospholipid in a cell

1:1

Role of cholesterol in cell membrane

Prevent overly dense packing of FA tails

How are extrinsic proteins connected to cellular membrane

Weak electrostatic forces

Glycoproteins + Glycolipid

Many membrane proteins and some lipids are conjugated with short chains of polysacharides. They form the glycocalyxR

Role of glycocalyx

Cell recognition, intercellular adhesion formation, adsorption of molecules to cell surface, mechanical + chemical protection

3 mechanisms of external information transport to cell interior

1. Lipid soluble messengers pass through cell to bind to intracellular receptor

2. Messenger binds to cell surface, activating cytoplasmic second messengers to pass on information

3. Nerve cells release neurotransmitters that bind to nerve cell or muscle cell opening an ion channel for membrane depolarization

Contents of the nucleus

DNA, nucleoprotein, RNA

Types of nucleoprotein

• Histone protein: bind to DNA and control DNA coiling

  • Non-histone protein: include enzymes for DNA and RNA synth, regulatory proteins

Types of chromatin inside the nucleus

Heterochromatin: Tightly coiled inactive chromatin in irregular clumps around periphery

Euchromatin - DNA active in RNA synthesis

Role of nucleoli

Sites of ribosomal RNA synthesis and ribosome assembly - seen in cells with highly active protein synthesis

Nuclear envelope

2 layers of membrane with intramembranous space

• Outerlayer continuous with RER

  • Inner aspect is nuclear lamina, consiting of polypeptides called lamins - link membrane proteins and heterochromatinR

Role of nuclear pores

Allow inner and outer membranes to be continuous - allow exchange of metabolites, macromolecules, ribosomal subunits between nucleus and cytoplasm

Composition of ER

Interconnecting network of membranous tubules, vesicles, and flattened sacs (cisternae)

rER function

Exported protein + lysosomal protein production

What is synthesized on free ribosomes

Proteins destined for the cytoplasm, nucleus, and mitochondria

Function of sER

Lipid biosynthesis and membrane synthesis and repair

Golgi function

Processing and packaging of macromolecules for export out of cell or storage for use inside cell

Role of transition vesicles

Shuttle rER molecules to Golgi

Lysosomes

Membrane bound organelles with around 50 digestive enzymes to breakdown macromolecules

Classes of lysosomes

Primary - only digestive enzymes

Secondary - enzymes and molecules that the cell must break down

what happens to products of lysosomal digestion

Released otuside the cell or absorbed and used again by the cell

Peroxisomes

Membrane bound organelles with different enzymes than lysosomes: they have oxidases

Unique feature of mitochondria

Contains one or more stands ot circular DNA and ribosomes, allowing for synthesis of 37 of its own proteins. It also allows the mitochondria to undergo self-replication

Cytoskeleton structural elements

Microfilaments, intermediate filaments, microtubules

Microfilaments

Fine strands of actin

Intermediate filaments

Immediate size - proteins have purely structural function

Microtubules

Largest cytoskeleton component, originate from centriole found in th centrosome

Centrosome components

2 centrioles - each centriole consists of nine triplets of microtubules in a cylindrical manner

4 functions of the cytoskeleton

1. Provides structural support to plasma membrane, cellular organelles, and some cytosolic enzyme systems

2. Provides means for movement of intracellular organelles, PM, and other cytosol constituents necessary for routine functions of all cells

3. Provides locomotor mechanism for ameboid movements and specialized motile structures such as cilia and flagella

   1. Responsible for contractility in specialized tissues such as muscle

Result of mitosis

2 identical daughter cells

Cell cycle phases

G1 - cell differentiation and specialized functions performed as part of whole tissue

S phase - synthesis phase, DNA replication occurs

G2 - Period which cells prepare for mitotic division

M phase - Mitosis

G0 - Phase of continuous differentiated function

4 phases of mitosis

Prophase, metaphase, anaphase, telophase

Prophase

Chromosome condensation, nucleoli disappear, dissolution of nuclear envelope. Centrioles migrate to opposite poles of cell

Metaphase

Each duplicated chromosome becomes attached to mitotic spindle and are arranged in the plane of the spindle equator known as the metaphase plateA

Anaphase

Centrioles pulled apart and the chromatids of each duplicated chromosome are drawn to opposite ends of the spindle. By the end, two groups of identical chromosomes are clustered at opposite ends of the cell

Telophase

Nuclear envelope reassembles, nucleoli becomes apparent, cytoplasmic division occurs

Location of meiosis

Only in germ cells of the gonads during formation of gametes

How many cel division processes of meiosis are there

2

First meiotic division

Results in 2 non-identical daughter cells. No chromatid separation, but there is exchange of genetic information between chromatids of homologous pairs of duplicated chromosomes

Second meiotic division

Spitting or rearranged duplicated chromosomes to liberate chromatids which migrate to opposite poles of the spindle

Product of meiosis

4 non-identical daughter cells

2 mechanisms of cell death

Apoptosis, necrosis

Apoptosis

Method of cell death is an active process, requiring the expenditure of energy. Has various triggers and does not incite an inflammatory reaction

Necrosis

Cell death in pathological conditions. Characterized by the inability of cells to produce energy to maintain homeostasis and incites an inflammatory reaction

Apoptosis mechanism

1. Cell receives signal to initiate apoptosis

2. Condensation of nuclear chromatin (pyknosis)

3. Cell shrinks away from neighbors with loss of cell-cell contacts

4. Nuclear material breaks into fragments (karyorrhexis) which is accompanied by dissolution of nuclear membrane

5. Cytoplasmic blebs break away from cell surface and eventually the entire cell breaks up (karyolysis)

6. Macrophages phagocytose cellular debris

What is epithelia

Group of tissues which cover exposed body surfaced and line body cavities, tubes, and organs

Roles of epithelial

1. Selective diffusion

2. Absorption

3. Secretion

4. Physical protection

5. Containment

One function of epithelia is containment - what does this mean?

Epithelia forms a barrier on the body, preventing loss of fluid or pathogens from entering our body

General anatomy of epithelia

- Form continues sheets comprising of one or more layers.

- Closely bound to each other by cell junctions

- Supported by basement membrane (separates epithelia from underlying supportive surfaces)

How do the epithelia receive oxygen and metabolites

Via diffusion from supporting tissues. Basement membrane is never penetrated by blood vessel

How is epithelia classified

1. Number of cell layers

2. Shape of component cells

3. Presence of surface specializations

Simple epithelium

Single layer of epithelial cells on basement membrane

Role of simple epithelium

Found at interfaces of selective diffusion, absorption, or secretion (but no protection against mechanical force)

Stratified epithelium

Several layers of cells sit on basement membrane

Squamous epithelium

Flattened cells

Simple squamous epithelium

Flattened, irregularly shaped cells, forming continuous surface

Role of simple squamous epithelium

Allows for passive transport (diffusion) of gases or fluids

Where can simple squamous epithelium be found?

- Lines blood vessels (endothelium)

- Lines body cavities (mesothelium): pleural (lung), pericardial (heart), peritoneal (abdominal)

- Alveoli of lungs

- Bowman's capsule in kidney (allowing for nutrients from glomerulus)

What epithelium is this? What is the strucure?

Simple squamous epithelium. Structure is Bowman's capsule from the kidney

What epithelium is this? What is the structure?

Simple squamous epithelium. Structure is alveoli from the lung

simple cuboidal epithelium

Intermediate between simple squamous and simple columnar epithelium. Epithelial cells appear square, with a round nucleus

Role of simple cuboidal epithelium

Lines small ducts and tubules - used for excretory, secretory, or absorptive functions

Where can simple cuboidal epithelium be found?

- Kidney tubules;

- ducts and secretory portions of small glands

- ovary surface

What type of epithelium is shown on the right side? What is the structure

Simple cuboidal. Structure is kidney tubules (see glomerulus + bowman's capsule to the left)

simple columnar epithelium

Similar to cuboidal, but cells are taller and appear like columns, perpendicular to basement membrane. Nucleus is often elongated, and location is variable in the cytoplasm

Function of simple columnar epithelium

absorption and secretion

Where is simple columnar epithelium found?

Digestive tract (colon, small intestine, stomach)

What type of epithelium is this?

Simple columnar

Simple columnar ciliated

Simple columnar epithelia with cilia on apical surface

Role of cilia

Beat in wave like manner - generating a current to propel fluid into one direction along epithelial surface

What is often seen among ciliated cells?

Non-ciliated cells, usually with a secretory function (like goblet cells)

Are cilia seen on stratified cells?

Never

Where is simple columnar ciliated epithelium found?

Fallopian tubes

What type of epithelium is this?

Simple columnar ciliated. This is the fallopian tubes

Pseudostratified columnar ciliated epithelium

Psuedostratified = has the apperance of stratified epithelia, but is one cell layer to basement membrane. Nucleus location is variable. Nuclei is mainly found on basal side of cells. Have cilia

Where is Pseudostratified columnar ciliated epithelium found?

Only in the respiratory tract (lung, trachea). AKA respiratory epithelium

What type of epithelium is this? Where is it found?

Pseudostratified columnar ciliated epithelium. This is in respiratory tract (image is from trachea). Notice how nuclei are in the basal part of cell.

Role of stratified epithelium

Mainly protective function. Ill-suited for absorption.

How is stratified epithelium classified?

Based on cell type on apical surface. Most cells on basal surface are always cuboidal

Stratified cell sloughing

Apical cells have less access to nutrients, and will slough off. They are quickly replaced. Because of this, cancer drugs (targeting rapidly dividing cells) often harm stratified epithelium

Stratified squamous epithelium

Variable number of cells, with squamous cell on apical surface. Basal cells divide continiusly

Where is stratified squamous epithelium found?

- Oral cavity

- Pharynx

- Esophagus

- Anal canal

- Uterine, cervix, vagina

What type of epithelium is this?

Stratified squamous non-keratinized epithelium

Stratified squamous keratinized epithelium

Specialized form of stratified squamous epithelium with layer of keratin (protein)

How is keratin formed?

Keratinization - During maturation, epithelial cells accumulate cross-linked cytoskeletal proteins

Role of keratin

Withstands constant abrasion and desiccation

What type of epithelium is this? Where is it found?

Stratified squamous keratinized epithelium. This is found on skin

Stratified cuboidal epithelium

Thin, stratified epithlium which usually consists of 2-3 layers of cuboidal/low columnar cells

Where is stratified cuboidal epithelium found?

Larger ducts of exocrine glands (esp. salivary glands)

What type of epithelium is this? Where is it found?

Stratified cuboidal epithelium. This is from a salivary gland

Transitional epithelium

Form of stratified epithelium - has both features of stratified squamous and cuboidal epithelium. Top layer of cells are called "umbrella cells" - often multinucleated

Function of urothelium

Bladder needs to stretch when filling with urine. When stretched, cells look squamous, After urination, cells look more cuboidal

Where is transitional epithelium found?

Found only in the urinary tract. AKA urothelium

What type of epithelium is this? Where is it found?

Transitional epithelium. Found in urinary tract

Metaplasia

change from one type of epithelium to another