LESSON 2: The Tissue Level of Organization

Tissues

• these are 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).

Histology

• It is the study of the microscopic anatomy of cells and tissues – it is a branch of pathology.

• Of the 10 trillion cells in our body, no single cell type can said to be “typical”. A trained histologist can recognize over 200 distinct human cell types under the microscope and is able to distinguish a cell from pancreatic tissue as opposed to a cell from the skin.

• Each cell type has features particular to its function.

Epithelial tissues, Connective tissues, Muscular tissues, Nervous tissues

• The 4 Basic Tissues

• Of all the cells in the body, they combine to make only 4 basic tissue types: (what are those 4?)

Epithelial tissues

• The 4 Basic Tissues

• cover body surfaces and form glands and line hollow organs, body cavities, and ducts.

Connective tissues (C.T.)

• The 4 Basic Tissues

• protect, support, and bind organs.

Fat

is a type of C.T. that stores energy.

connective tissues

Red blood cells, white blood cells, and platelets are all ___________ (what type of tissue?)

Muscular tissues

• The 4 Basic Tissues

• generate the physical force needed to make body structures move. They also generate heat used by the body.

Nervous tissues

• The 4 Basic Tissues

• detect changes in the body and respond by generating nerve impulses.

Endoderm, Mesoderm, Ectoderm

Tissues of the body develop from three primary germ layers: (what are those 3 layers?)

Epithelial tissues

what type of tissue is from all three germ layers

connective tissue, muscular tissue

what type of tissues (2) are derived from mesoderm?

Nervous tissue

what type of tissue is developed from ectoderm?

ectoderm

• __________ develops into:

  • nervous tissue

  • outer skin layer (including hair and nails)

  • parts of:

    • sense organs

    • mouth

    • sinuses

    • teeth

endoderm

• ________ develops into parts of:

  • digestive tract

  • lungs and respiratory tract

  • bladder

mesoderm

• __________ develops into

  • muscles

  • bones

  • cartilage

  • blood and vessels

  • lymph tissue

  • part of:

    • kidneys

    • gonads

Epithelium

• ___________ is used to line surfaces and form protective barriers.

• __________ is also good at secreting things like mucous, hormones, and other substances.

• All ________ have a free apical surface and an attached basal surface.

basal layer

The ___________ of the epithelium secretes a basal lamina; the underlying C.T. secretes a reticular lamina.

basal lamina

The basal layer of the epithelium secretes a __________; the underlying C.T. secretes a reticular lamina.

reticular lamina

The basal layer of the epithelium secretes a basal lamina; the underlying C.T. secretes a _________.

noncellular basement membrane

Together the basal lamina and the reticular lamina form a ___________________ on which the epithelium sits.

Epithelia

are named according to the shape of their cells, and the thickness or arrangement of their layers (of cells).

simple, pseudostratified, stratified

naming epithelium based on arrangement of layers

squamous, cuboidal, columnar

naming epithelium based on cell shape

squamous

• Naming epithelia according to shape

• Flat, wide “paving stone” cells

cuboidal

• Naming epithelia according to shape

• Cells as tall as they are wide

columnar

• Naming epithelia according to shape

• Cells taller than they are wide

simple

• Naming epithelia according to arrangement

• One layer. All cells in contact with basement membrane

pseudostratified

• Naming epithelia according to arrangement

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

stratified

• Naming epithelia according to arrangement

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

Naming epithelia

Naming epithelia

• Three different cell shapes x three different cell arrangements = nine possibilities. Two of these are not used. Add transitional (cells that change shape), and we’re back up to eight possible combinations.

• If different shapes are present in layers of cells, the epithelium is always named by the shape of cells in the apical (outermost) layer.

Simple Squamous Epithelium

• is composed of a single layer of flat cells found:

  • In the air sacs of lungs

  • In the lining of blood vessels, the heart, and lymphatic vessels

  • In all capillaries, including those of the kidney

  • As the major part of a serous membrane

• function: for easy permeability & diffusion

Simple Cuboidal Epithelium

• is composed of a single layer of cube shaped cells.

• It is often found lining the tubules of the kidneys and many other glands.

• function: for secretion

Simple Columnar Epithelium

• forms a single layer of column-like cells, ± cilia, ± microvilli, ± mucous (goblet cells).

• Goblet cells are simple columnar cells that have differentiated to acquire the ability to secrete mucous.

• this is found in respiratory tract and digestive tract

• functions:

  • goblet cells - for secretion of mucus

  • cilia - for protection & movement

simple cuboidal epithelium, kidney tubules

classify based on shape and number of layers, and what organ

free apical surface, attached basal surface

epithelia has two main parts, what are these?

basal lamina

what part of basement membrane is closely attached to the epithelium

reticular lamina

what part of basement membrane is next to the basal lamina

Pseudostratified Columnar Epithelium

• appears to have layers, due to nuclei which are at various depths. In reality, all cells are attached to the basement membrane in a single layer, but some do not extend to the apical surface.

• Ciliated tissue has goblet cells that secrete mucous.

• It is found in the upper respiratory tract

• function: since its found in upper respiratory tract, it functions more in secretion of mucous, protecting upper respiratory from dust.

Stratified Squamous Epithelium

• has an apical surface that is made up of squamous (flat) cells.

• The other layers have different shapes, but the name is based on the apical layer.

• The many layers are ideal for protection against strong friction forces.

• function: for protection

• found in skin

Stratified Cuboidal Epithelium

• has an apical surface made up of two or more layers of cube-shaped cells.

• Locations include the sweat glands and part of the ♂ (male) urethra

• it is not very common

Stratified Columnar Epithelium

is very rare, and for our purposes, hardly worth mentioning.

Transitional Epithelium

• The cells of _____________ change shape depending on the state of stretch in the tissue.

• The apical “dome cells” of the top layer (seen here in relaxation) are an identifiable feature and signify an empty bladder.

• In a full bladder, the cells are flattened.

• maximum volume of urine that can be stored in urinary bladder is 700-800 ml

• if urinary bladder is filled with urine, the epithelial lining is squamous (flat)

• when it is empty or umihi ka na, the epithelial lining is either cuboidal or columnar

stratified cuboidal, found in male urethra and sweat glands, absorption & secretion

Classify epithelium based on shape and number of layer, location, and function

Stratified squamous epithelium

• Although epithelia are found throughout the body, certain ones are associated with specific body locations.

• ____________ is a prominent feature of the outer layers of the skin.

Simple squamous

_______________ makes up epithelial membranes and lines the blood vessels.

Columnar

is common in the digestive tract.

Pseudostratified ciliated columnar

_____________________ is characteristic of the upper respiratory tract.

Transitional

____________ is found in the bladder.

Cuboidal

____________ lines ducts and sweat glands.

Endothelium

• Covering and Lining Epithelium

• is a specialized simple squamous epithelium that lines the entire circulatory system (including capillaries, blood vessels, veins, artery, and heart) from the heart to the smallest capillary – it is extremely important in reducing turbulence of flow of blood.

• lines blood vessels and heart

Mesothelium

• Covering and Lining Epithelium

• is found in serous membranes such as the pericardium, pleura, and peritoneum.

• Unlike other epithelial tissue, both are derived from embryonic mesoderm (the middle layer of the 3 primary germ layers of the embryo).

• lines serous membrane

mesoderm

all epithelial tissue comes from 3 germ layers except for endothelium & mesothelium, which comes from the ___________

Connective Tissues

• __________ are the most abundant and widely distributed tissues in the body – they are also the most heterogeneous of the tissue groups.

• They perform numerous functions:

  • Bind tissues together

  • Support and strengthen tissue

  • Protect and insulate internal organs

  • Compartmentalize and transport

  • Energy reserves and immune responses

Collagen

_____________ is the main protein of C.T. and the most abundant protein in the body, making up about 25% of total protein content.

Connective tissue

• __________ is usually highly vascular and supplied with many nerves.

• The exception is cartilage and tendon - both have little or no blood supply and no nerves.

connective tissues

• Although they are a varied group, all ___________ share a common “theme”:

  • Sparse cells

  • Surrounded by an extracellular matrix

extracellular matrix

• The __________ is a non-cellular material located between and around the cells.

• It consists of protein fibers and ground substance (the ground substance may be fluid, semifluid, gelatinous, or calcified.)

protein fibers, ground substance

• The extracellular matrix is a non-cellular material located between and around the cells.

• It consists of _________ and __________ (the ground substance may be fluid, semifluid, gelatinous, or calcified.)

Fibroblasts

• Common C.T. cells

• are the most numerous cell of connective tissues. These cells secrete protein fibers (collagen, elastin, & reticular fibers) and a “ground substance” which varies from one C.T. to another.

Chondrocytes

• Of the other common C.T. cells:

• make the various cartilaginous C.T.

Adipocytes

• Of the other common C.T. cells:

• store triglycerides.

Osteocytes

• Of the other common C.T. cells:

• make bone.

White blood cells

• Of the other common C.T. cells:

• are part of the blood.

g-actin

most common protein in cytosol

macrophages, neutrophils, mast cells, eosinophils, lymphocytes

There are 5 types of white blood cells (WBCs): (what are those?)

monocyte

largest WBC in peripheral blood and it is horse-shoe shape. this becomes macrophages

Macrophages

are the “big eaters” that swallow and destroy invaders or debris. They can be fixed or wandering.

Neutrophils

• are also macrophages (“small eaters”) that are numerous in the blood.

• increases when there is bacterial infection

• w/ pinkish or lilac granules

Mast cells, Eosinophils

these two play an important role in inflammation

basophil

• w/ purplish granules

• nasa granules yung histamine

• paglabas sa blood magiging mast cell

mast cells

• it is called basophils when inside the blood

• it has histamine

eosinophils

• increases when there is allergy and parasitism

• w/ orange granules

Lymphocytes

• secrete antibody proteins and attack invaders.

• appearance: almost occupying the whole cell

macrophage

• _________ = outside the blood

• monocyte = inside the blood

monocyte

• macrophage = outside the blood

• _________ = inside the blood

Langerhans cell

macrophage of skin

Kupffer cell

macrophage of liver

microglia

macrophage of nervous system

histiocyte

macrophage of connective tissue

osteoclast

macrophage of bone

dust cells

macrophage of lungs

T-lymphocyte

• bone marrow → thymus → blood

• for cellular immunity

• T4 - helper

• T8 - cytotoxic

• T8 attacks virus, tumor, and transplanted cells

• normal:

  • CD4 (T4) : CD8 (T8) = 2 : 1

• person with HIV:

  • CD4 (T4) : CD8 (T8) = 1 : 2

B-lymphocyte

• bone marrow → blood

• for humoral immunity

• produces antibodies

Collagen fibers, Elastin fibers, Reticular fibers

C.T. cells secrete 3 common fibers: (what are these?)

Embryonic connective tissue, Mature connective tissue

2 Connective Tissue Classification

Mesenchyme, Mucous connective tissue

There are 2 Embryonic Connective Tissues: (what are these?)

Mesenchyme

Embryonic Connective Tissue that gives rise to all other connective tissues.

mucous connective tissue

Embryonic Connective Tissue that (Wharton's Jelly) is a gelatinous substance within the umbilical cord and is a rich source of stem cells.

mesenchymal connective tissue

identify

mucous connective tissue

identify

Areolar Connective Tissue

• Loose Connective Tissues

• is the most widely distributed in the body. It contains several types of cells and all three fiber types.

• It is used to attach skin and underlying tissues, and as a packing between glands, muscles, and nerves.

• most easily identified because it is widely distributed

triglycerides

type of fat stored in adipose tissue

Adipose tissue

• Loose Connective Tissues

• is located in the subcutaneous layer deep to the skin and around organs and joints.

• It reduces heat loss and serves as padding and as an energy source.

Reticular connective tissue

• Loose Connective Tissues

• is a network of interlacing reticular fibers and cells.

• It forms a scaffolding used by cells of lymphoid tissues such as the spleen and lymph nodes.

Dense Irregular Connective Tissue

• Dense Connective Tissues

• consists predominantly of fibroblasts and collagen fibers randomly arranged.

• It provides strength when forces are pulling from many different directions.

Dense regular Connective Tissue

• Dense Connective Tissues

• comprise tendons, ligaments, and other strong attachments where the need for strength along one axis is mandatory (a muscle pulling on a bone).

Elastic Connective Tissue

• Dense Connective Tissues

• consists predominantly of fibroblasts and freely branching elastic fibers.

• It allows stretching of certain tissues like the elastic arteries (the aorta).

Cartilage

is a tissue with poor blood supply that grows slowly. When injured or inflamed, repair is slow.

Hyaline cartilage

• cartilage

• is the most abundant type of cartilage; it covers the ends of long bones and parts of the ribs, nose, trachea, bronchi, and larynx.

• It provides a smooth surface for joint movement.