Anatomy lecture 2

What are tissues

They are groups of cells with similar structures and functions

What are the 4 primary types of tissues

1. Epithelial tissue

2. Connective tissue

3. Nervous tissue

4. Muscle tissue

Where are epithelial tissues located

They are found in body coverings, body linings and glandular tissues

What is the function of epithelial tissue

1. Protection

2. Absorption

3. Filtration

4. Secretion

PAFS

What are the 4 components of the cell theory

1. Cell = basic structural and functional unit of living organisms

2. Activity of an organism depends on collective activities of cells

3. By the principle of complementarity, biochemical activities of cells are dictated by their anatomy (structure) with determines their physiology (function)

4. Continuity of life depends on the cellular basis

What are the 4 elements that compose most cells

Carbon

Hydrogen

Nitrogen

Oxygen

Cells are composed of around 60% of water

What are the 3 main regions of cells

Plasma membrane

Nucleus

Cytoplasm

What is the plasma

It’s the transparent barrier for cell

It contains cell contents

It separates the cell contents from the surrounding environment

Important facts of epithelial tissues

1. Cover and line the body surfaces

2. It often forms sheets with one free surface called the apical surface and an anchored surface called the basement membrane

3. It’s avascular which means it doesnt get blood supply since it doesnt contain blood vessels

4. If it is well nourished, it regenerates easily

How do we classify epithelia

1. By the number of cell layers

2. By the shape of the cells

Classify epithelia by the number of cell layers

Simple → 1 layer of cells

Stratified → more than 1 layer of cells

Classifying epithelia by the shape of cells

Squamous → flattened (think fish scales)

Cuboidal → cube shaped (think dice)

Columnar → shaped like columns

Function squamous depending on the number of layers

In 1 layer (simple): It allows for diffusion and filtration and secretion in serous membranes

In more than 1 layer (stratified): It serves as protection where the transitional epithelium is modified into stratified squamous which stretches to accomodate distension of urinary structures

Function of cuboidal and columnar depending on the number of layers

In one layer: it serves for secretion and absorption where ciliated types propel mucus or reproductive cells

In multiple layers: It serves as protection even tho it’s very rare to find these tissue types in human

Function and structure of simple epithelia (in general)

• Very thin so it’s not suited for protectiom

• Functions in absoption, secretion and filtration since fluids can easily pass across.

Function and structure of simple squamous epithelium

• Single layer of flat cells (remember squamous = fish scales due to being flattened)

• Located where it can form membranes = lines air sacs of lungs, form walls of capillaries, form serous membranes (serosae) that line and cover organs in ventral cavity

• Functions in filtration or diffusion

Function and structure of simple cuboidal epithelium

• It’s a single layer of cubelike cells

• Located in: glands and their ducts, forms walls of kidney tubules and cover the surface of ovaries

Structure and function of of simple columnar epithelium

• It’s a single layer of tall cells and goblet cells secrete mucus

• Located in the lining of the digestive tract from stomach to anus. The mucous membranes also called mucosae line the body cavities opening to the exterior.

What is a pseudostratified columnar epithelium

It’s when all cells rest on a basement membrane and there is a single layer (so it is simple) but some cells are shorter than other which gives a false (hence the pseudo) impression of stratification

It is located in the respiratory tract where it is ciliated and known as pseudostratisfied ciliated columnar epithelium

Function: Absorption or secretion

Stratified squamous epithelium

Most common stratified epithelium

Named this way due to the squamous cells present at the free apical surface

Function: Protective covering where friction is common

Located at the lining of skin (outer portion), the mouth and esophagus

Stratified cuboidal and columnal epithelium

• 2 layers of cuboidal cells or more

• For the stratisfied columnar epithelium: the cells at the apical surface are columnar while the ones beneath vary in size and shape

• Both are rare in the human body and are found in the ducts of the large glands

What is transitional epithelium

Note that it’s a stratisfied epithelium but it can change shapes when the tissue is being stretched (=transitions between shapes)

• It’s composed of modified stratified squamous epithelium

• The shape of cells depends on the amount of stretching

• Function: Involved in stretching and the ability to return to normal shape after stretching

• Located in the lining of urinary system organs (transition between when the bladder is full and when empty)

Glandular epithelia

• When one or more cells are respnsible for secreting a certain product

• Secretions contain protein molecules in aqueous fluid and is an active process

What are the 2 major gland types that develop from epithelia sheets

1. Endocrine glands: Ductless. It secretes hormones which diffuse into blood vessels such as thyroid, adrenals and pituiary glands

2. Exocrine glands: Contains ducts in which secretions empty through to the epithelial surface such as sweet and oil gland, liver and pancreas

Connective tissues function and location

• Found everywhere in the body to connect body parts and includes the most abundant and widely distributed tissues

• Function: Protection, Supporting, Cushioning and Insulating

PSIC

Characteristics of connective tissues

Contains variations in blood supply compared to other tissues meaning depending on the type of connective tissue

• Some tissue types are well vascularized = lot of blood

• Some have poor blood supply or are avascular

Composed of extracellular matrix which is the nonliving material that surrounds living cells

What are the 2 main elements of extracellular matrix

1. Ground substance which is mostly water with adhesion proteins and polysaccharide molecules

2. Fibers which cann be separated into 3 types:

• Collagen (white) fibers

• Elastic (yellow) fibers

• Reticular fibers (which is a type of collagen)

Rank the type of connective tissue from most rigid to the softest/fluid

1. Bone

2. Cartilage

3. Dense connective tissue

4. Loose connective tissue

5. Blood

Composition and function of bones

They’re composed of:

• Osteocytes (bone cells) which sit in lacunae (cavities)

• Hard matrix of calcium salts

• Large number of collagen fibers

Function:

• Protect and support the body

Composition and location of cartilage

Less hard and more flexible than bones

Found only in a few placeins body and not everywhere

Major cell type of cartilage = Chondrocyte (cartilage cell)

3 types:

• Hyaline cartilage

• Fibrocartilage

• Elastic cartilage

Define hyaline cartilage

• Most widespread = abundant type of cartilage

• It’s abundant collagen fibers hidden by a glassy rubbery matrix

• Located in:

Trachea

Atttaches ribs to teh breastbone

Covers the end of long bones

Entire fetal skeleton before birth

Epiphyseal (active site responsible for making bones grow longer) well plates in long bones

Define elastic and fibrocartilage

Elastic cartilage:

• Povides electricity and is located unto supporting the external ear

Fibrocartilage:

• Highly compressible and it is located between the vertabraes of the spinal column to form cushion like discs

What are the 2 categories of connective tissues

1. Dense connective tissue (dense regular fibrous tissue)

2. Loose connective tissue

What is matrix and what is it composed of

It just means stuff that other things are embedded/composed of.

Extracellular matrix is made of 2 things:

1. Ground substance which is gel like substance

2. Fibers which are protein strands that give structural support. Ex: collagen fibers for strength

Define dense connective tissue

The main matrix element = collagen fibers made by fibroblasts (cell that make fibers)

For the dense regular fibrous tissue, the connective tissues are located at:

• Tendons which attach skeletal muscle to the bone

• Ligaments which attach bone to bone at joints and are more elastic than tendons

For the dense irregular fibrous tissues, the connective tissues are located at:

• Dermis which are the lower layers of the skin

Define loose connective tissue

• Softer = have more cells and less fibers than other connective tissues except blood

There exists 3 types of connective tissues:

• Aerolar

• Adipose

• Reticular

Define aerolar connective tissue