Prerequisites（预备知识）

Difference Between Exocrine and Endocrine

 Article Link: http://www.differencebetween.net/science/health/difference-between-exocrine-and-endocrine/

What is the endocrine system?

Endocrine is the collection of glands which produce hormones to regulate processes such as growth and development, reproduction and sexual function, metabolism and mood and sleep.

The  endocrine system made up of following glands:

• pituitary gland

• pancreas

• thyroid gland

• adrenal glands

• parathyroid glands

• Reproductive glands such as ovaries & testicles

The word Endocrine originated from the Greek words “‘endo’ meaning within and ‘crinis’  meaning ‘secrete.  These glands remove materials from the blood and process and secretes necessary product for use elsewhere in the body. Hormones produced by these glands circulate throughout the body and each hormone is marked toward specific organs and tissues.

Diseases of the endocrine system

Diseases occur when the hormone levels are either too high or too low.

When does this occur?

• If the body does not respond to hormonal changes appropriately.

• Stress

• Infection

• Electrolyte imbalance

Examples of endocrine diseases are :

1. Diabetes (most common) -improper process glucose due to the lack of insulin

2. Hypothyroidism – Insufficient amount of thyroid hormone produced

3. Hypoglycemia – low blood glucose

What is the exocrine system?

Similar to endocrine system, exocrine system is made up of glands that produce and secrete substances to protect or lubricate the human body.

The  Exocrine system made up of following glands:

• Sweat Glands

• Salivary

• Mucous

• Mammary

• Gastric

• Prostate

• Bile

• Ceruminous

• Sebaceous

• Lacrimal

The substances produced by these exocrine glands travel through ducts. They are deposited onto epithelial surfaces: These epithelial cells have three unique shapes:

1. Squamous

2. Columnar

3. Cuboidal

Diseases of the Exocrine system

There are numerous conditions may affect the exocrine system and lead to over or under secretion of these glands.

When does this occur?

• Infections

• Ulcer

• Obstructions

• Genetic conditions

• Cysts

• Cancer

• Tumors

The endocrine system and the exocrine system are closely associated with each other and there are times, some of the diseases witnessed in the endocrine system are also can been identified in the exocrine system.

Examples of endocrine diseases are :

1. Acromegaly: Over production of  growth hormone

2. Addisons Disease: less corticosteroids

3. Cystic Fibrosis: abnormally mucus production

Exocrine vs Endocrine

Exocrine glands are glands that secrete their products through the ducts, and discharge it into the external environment, to organs or the outside the body. Endocrine glands are ductless, therefore the secreted hormones are released into the interstitial spaces that surround the cells. The hormones are delivered to the nearest capillaries, and spread throughout the body. The responses are delayed because hormones must first travel through the blood to reach the target organs. The duration is longer because the kidneys filter the blood. The functions of the endocrine are interrelated. Many of the hormones generated serve to alter the work of other endocrine hormones.

Exocrine glands differ from endocrine glands, because they have ducts that deliver the products in the superficial part of the body, such as the skin, or in the inner part where they are necessary, such as the pancreatic juice that is carried into the intestine to aid digestion. The glands that are found in the body are mostly exocrine glands. Examples of exocrine glands are sweat, saliva and mammary glands, as well as oil and enzymes. There are glands which function as both endocrine and exocrine glands.

The endocrine system is also one of the body’s most important systems, especially with the control of the body’s functions. This is how the body communicates and coordinates with the nervous system, reproductive system, pancreas, liver, kidneys and fat to maintain balance, or homeostasis, with reproduction, growth and development, and energy levels and responses to external stress and injury. Endocrine glands produce hormones that can be used inside the body. The endocrine transmits the hormonal messages to cells by secreting them into the blood and extracellular fluid. A receptor is needed in order to receive the message transmitted. The target points may be cells, tissues or organs.

Summary:

1. Exocrine glands have ducts to carry secreted subtances to the rest of the body, while endocrine glands are ductless.

2. Exocrine glands release subtances into the external environment, or outside of the body. Endocrine hormones are released into the internal environment, or inside of the body.

3. Exocrine glands have sub-classifications.

4. Endocrine response is slower because hormones travel through the blood.

5. The duration in endocrine transmission is prolonged because kidneys have to filter the blood.

Read more: Difference Between Exocrine and Endocrine | Difference Between http://www.differencebetween.net/science/health/difference-between-exocrine-and-endocrine/#ixzz5C5qcTbyf

What is human body tissue?

Article Link：https://en.wikipedia.org/wiki/Tissue_(biology)

Human body tissue makes up organs and other body parts. There are four main types of tissue: muscle, epithelial, connective and nervous. Each is made of specialized cells that are grouped together according tostructure and function. Muscle is found throughout the body and even includes organs such as the heart.

In biology, tissue is a cellular organizational level between cells and a complete organ. A tissue is an ensemble of similar cells and their extracellular matrix from the same origin that together carry out a specific function. Organs are then formed by the functional grouping together of multiple tissues.

The English word is derived from the French tissu, meaning something that is woven, from the verb tisser, "to weave".

The study of human and animal tissues is known as histology or, in connection with disease, histopathology. For plants, the discipline is called plant anatomy. The classical tools for studying tissues are the paraffin block in which tissue is embedded and then sectioned, the histological stain, and the optical microscope. In the last couple of decades,^{[clarification needed]} developments in electron microscopy, immunofluorescence, and the use of frozen tissue sections have enhanced the detail that can be observed in tissues. With these tools, the classical appearances of tissues can be examined in health and disease, enabling considerable refinement of medical diagnosis and prognosis.

Animal tissues

PAS diastase showing the fungus Histoplasma.

Animal tissues are grouped into four basic types: connective, muscle, nervous, and epithelial. Collections of tissues joined in structural units to serve a common function compose organs. While all animals can generally be considered to contain the four tissue types, the manifestation of these tissues can differ depending on the type of organism. For example, the origin of the cells comprising a particular tissue type may differ developmentally for different classifications of animals.

The epithelium in all birds and animals is derived from the ectoderm and endoderm with a small contribution from the mesoderm, forming the endothelium, a specialized type of epithelium that composes the vasculature. By contrast, a true epithelial tissue is present only in a single layer of cells held together via occluding junctions called tight junctions, to create a selectively permeable barrier. This tissue covers all organismal surfaces that come in contact with the external environment such as the skin, the airways, and the digestive tract. It serves functions of protection, secretion, and absorption, and is separated from other tissues below by a basal lamina.

Connective tissue

Main article: Connective tissue

Connective tissues are fibrous tissues. They are made up of cells separated by non-living material, which is called an extracellular matrix. This matrix can be liquid or rigid. For example, blood contains plasma as its matrix and bone's matrix is rigid. Connective tissue gives shape to organs and holds them in place. Blood, bone, tendon, ligament, adipose and areolar tissues are examples of connective tissues. One method of classifying connective tissues is to divide them into three types: fibrous connective tissue, skeletal connective tissue, and fluid connective tissue.

Muscular tissue

Main article: Muscle tissue

Muscle cells form the active contractile tissue of the body known as muscle tissue or muscular tissue. Muscle tissue functions to produce force and cause motion, either locomotion or movement within internal organs. Muscle tissue is separated into three distinct categories: visceral or smooth muscle, found in the inner linings of organs; skeletal muscle, typically attached to bones, which generate gross movement; and cardiac muscle, found in the heart where it contracts to pump blood throughout an organism.

Nervous tissue

Main article: Nervous tissue

Cells comprising the central nervous system and peripheral nervous system are classified as nervous (or neural) tissue. In the central nervous system, neural tissues form the brain and spinal cord. In the peripheral nervous system, neural tissues forms the cranial nerves and spinal nerves, inclusive of the motor neurons.

Epithelial tissue

Main article: Epithelium

The epithelial tissues are formed by cells that cover the organ surfaces such as the surface of skin, the airways, the reproductive tract, and the inner lining of the digestive tract. The cells comprising an epithelial layer are linked via semi-permeable, tight junctions; hence, this tissue provides a barrier between the external environment and the organ it covers. In addition to this protective function, epithelial tissue may also be specialized to function in secretion, excretion and absorption. Epithelial tissue helps to protect organs from microorganisms, injury, and fluid loss.

Functions of epithelial tissue:

• The cells of the body's surface form the outer layer of skin.

• Inside the body, epithelial cells form the lining of the mouth and alimentary canal and protect these organs.

• Epithelial tissues help in absorption of water and nutrients.

• Epithelial tissues help in elimination of waste.

• Epithelial tissues secrete enzymes and/or hormones in the form of glands.

There are many kinds of epithelium, and nomenclature is somewhat variable. Most classification schemes combine a description of the cell-shape in the upper layer of the epithelium with a word denoting the number of layers: either simple (one layer of cells) or stratified (multiple layers of cells). However, other cellular features, such as cilia may also be described in the classification system. Some common kinds of epithelium are listed below:

• Simple squamous epithelium

• Stratified squamous epithelium

• Simple cuboidal epithelium

• Transitional epithelium

• Pseudostratified columnar epithelium (also known as Ciliated columnar epithelium)

• Columnar epithelium

• Glandular epithelium

• Ciliated columnar epithelium

Fixation Artefacts(固定伪影）

Article Link: http://stainsfile.info/StainsFile/prepare/fix/agents/artefactdef.htm

Artefacts (or artifacts) are human made items or the results of human activity. Fixation artefacts are consequently changes brought about in the tissue as a result of human activity, i.e. putting some tissue in a fixative.

From that definition, fixation itself could be considered to be an artefact, as it is a change brought about by human activity, and sometimes that comment is made. It is certainly true that fixation alters the tissue state: it ceases to be a dynamic system and becomes static, with most chemical processes and physical structures suspended in the state they were when the fixative's chemicals encountered them. Despite that, a lot can be determined by examining that snapshot in time which is represented by a microscope section.

More particularly however, artefacts are usually defined as the unwanted effects of a process, including fixation. In practice these unwanted effects are largely restricted to a few items such as deposits from the fixative or its reactions with tissue components, and the physical effects of fixation we would prefer to do without, such as detectable shrinkage, both at the gross and microscopic levels; the hardening of some tissues which causes chatters parallel to the knife edge; and the brittleness from some fixatives which results in shattering and cracking during sectioning.

There are two deposits in particular that we may encounter fairly often. Formalin pigment, or acid formaldehyde hematein, is frequently seen as fine granules, particularly in bloody tissues, and mercury pigment is invariably encountered in tissues fixed with mercuric chloride. Both are easily removed.

Although, strictly speaking, it is not a fixation artefact, the removal of triglycerides – fats – is a consequence of the failure of the fixative to render them unaffected by subsequent reagents. Most fixatives are deficient in this area, and blank holes are often seen where there was, in life, fat globules.

Not too many years ago a new artefact began to be mentioned, and was named the parched earth effect. It quickly became apparent that this was not a previously undetected artefact, but was, in fact, the undesirable effects of warm ethanol fixation. It began to be seen when more laboratories switched to processing times of less than 24 hours from biopsy to diagnostic report. This can only be done with paraffin sections if each step is cut to the absolute minimum. Unfortunately, many laboratories did not give adequate time for the most fundamental step, fixation, to be adequately effective and protect the tissue. The result was that fixation was completed in subsequent steps with (warmed) ethanol. Parched earth artefact, then, is just the poor quality fixation obtained with ethanol, exaggerated by applying it warm to speed up dehydration.