Biology 211Anatomy & Physiology I

Histology

The study of tissues

Recall:

SYSTEMS are composed of one or more organs, all serving a common function

ORGANS are composed of one or more types of tissues, all serving a common function

TISSUES are composed of one or more types of cells and their products, all serving a common function

The study of structure at the level of tissues is called histology.

All tissues: -

-

With only a few, rare exceptions, all organs of the human body are composed of four types of tissue:

lines internal and external surfaces, including hollow organs. Also forms glands.

provides support and fills spaces

produces movement

carries and integrates electrical information

Each of these can have one or more subtypes

Epithelium

- Covers body surfaces (e.g. skin, cornea)

- Lines body cavities (e.g. peritoneal cavity, pericardial cavity

- Lines insides of hollow organs (e.g. stomach, heart, lung. aorta, oviduct)

- Forms glands (e.g. sweat glands, pancreas, salivary glands)

Characteristics of Epithelium

- Highly cellular, with very little extracellular matrix

- Cells form close contacts with each other

- Avascular

- High capacity for regeneration

Functional characteristics of epithelia depend on the cells, rather than the extracellular matrix which is unspecialized

Epithelium always supported by connective tissueand separated from it by a basement membrane.Depends on connective tissue for vessels, nerves, etc. Epithelium Basement membrane Connective tissue

Mucous Membrane orSerous Membrane

Epithelium

Different types for different functions.

Classified according to:a) Number of layers of cells

b) Shape of cells in the top layer

Single layer = Two or more layers =

Actually one layer but looks like more =

Flat = Cube-shaped = Taller than wide =

Change shape from squamous to cuboidal =

Epithelium

Number of layers Shape of surface cells

Squamous Simple CuboidalStratified ColumnarPseudostratified Transitional

Simple Squamous Epithelium

Simple Cuboidal Epithelium

Simple Columnar Epithelium

Pseudostratified Columnar Epithelium

Stratified Squamous Epithelium

Stratified Cuboidal Epithelium

(Stratified) Transitional Epithelium

Epithelium

No good examples of stratified columnar epithelium. Found only in parts of the male reproductive system

Epithelium also forms all glands in the body

Glands classified by

a) Whether or not they have ducts

b) Their method of secretion

Yes = Duct carries product to surfaceNo = Product secreted into surrounding extracellular matrix, picked up by blood vessels

Product released from undamaged cells Top part of cell lost during secretion Entire cell lost during secretion

Exocrine glands also classified by

c) Shape, and whether or not either the duct and/or the secretory part branches

Characteristics of Connective Tissue

- Lots of extracellular matrix; Relatively few cells

- Cells usually do not communicate with each other

- Highly vascular

- Different types of CT all arise from embryonic mesenchyme

Functional characteristics of connective tissues depend primarily on the extracellular matrix, which is often highly specialized, and not on the cells.

Connective Tissues

Common cells

Fibers

Connective Tissues

Ordinary connective tissues

Specialized connective tissues

Loose Areolar Connective Tissues

Adipose Connective Tissues

Dense Regular Connective Tissues

Dense Irregular Connective Tissues

Specialized Connective Tissues: Hyaline Cartilage

Specialized Connective Tissues: Elastic Cartilage

Specialized Connective Tissues: Fibrous Cartilage

Specialized Connective Tissues: Bone

Muscle Tissue:

Skeletal Muscle

Cardiac Muscle

Smooth Muscle

Very longUnbranched

ShorterBranched

ShortUnbranchedSpindle-shaped

Hundreds per cellPeripheral

One or two per cellCentral

One per cell

Central

Yes Yes No

Skeletal Cardiac Smooth Muscle Muscle Muscle

Myocytes

Nuclei

Striations

Skeletal

Cardiac

Smooth

More detail on muscle tissues and their cells when we discuss the muscular system

Nervous Tissue: (no subtypes)

1) Neurons (Excitable cells) Carry electrical signals from one place to another

2) Supporting Cells Nonexcitable Support & nourish neurons Glia in CNS Satellite cells Schwann cells More detail on nervous tissue and its cells when we discuss the nervous system