A&P Lab - Class 5: Histology I (epithelial and connective tissues)

What are the levels of organization in the body (ascending order from smallest unit to largest unit).

What are the levels of organization in the body (ascending order from smallest unit to largest unit).

Chemical - cellular - tissue - organ - system - organism

Which unit that composes the body is the smallest unit of life?

Cellular

True or False: Cells work independently

False. Cells do not operate independently, they work together.

Epithelial tissue

A tissue which covers the body, lines body cavities, and forms glands

Connective tissue

A tissue which binds and supports various organs

Muscle tissue

Contractile tissue

Nervous tissue

Initiates and conducts electrochemical impulses

What are the four basic tissue types?

Epithelial, connective, muscular, nervous

What is a microtome?

The instrument that sections slide tissues

True or False: Only one tissue type at a time will be shown on a microscope slide

False. Some slides may be used to examine more than a single tissue type

What is the thinnest epithelium found in the human body?

Simple squamous epithelium

Where is the simple squamous epithelium present?

Areas with diffusion (and gas exchange). Ex:

• The heart

• Blood vessels

• Lymphatic vessels

• Forming capillary walls

Which type of cell resembles “fried eggs”?

Simple squamous

What is the function of simple cuboidal epithelium?

Secretion and absorption. Ex:

• Thyroid gland

• Kidney tubules

• Ducts of many glands

Function of simple columnar epithelia

Absorption and secretion. Ex:

• Stomach

• Small and large intestines

• Ducts if various glands (line)

Which cells have goblet cells?

Simple columnar epithelia

What is the role of goblet cells?

They produce mucus which acts as a lubricant and protective barrier. Very abundant in some parts of the digestive tract.

Characteristics of individual cells in stratified squamous epithelium

Bottom cells (closer to basement membrane) are often cuboidal, but top cells (closer to apical surface) are often squamous

Where are stratified squamous epithelia often found?

In areas of the body that are subject to “wear and tear”

Nonkeratinized vs. keratinized. What cell type could this be applied to?

Nonkeratinized: Absence of keratin Keratinozed: Presence of keratin This can be applied to stratified squamous epithelium

Keratinized cells at the surface of stratified squamous epithelial are (alive/dead)

Dead

In simple terms, what is a keratinized tissue?

Skin

What does transitional epithelium line? What makes this epithelium unique?

The urinary bladder, the urethra, the upper portion of the urethra. The thickness of this epithelium changes as it is subject to pressure.

Function of glandular epithelia. Where are they found?

Secretion. Found beneath the covering epithelia as single cells/cluster cells

What are glands specialized for?

To produce and secrete substances into ducts that open onto surfaces (exocrine glands) or secrete substances into body fluids (endocrine glands)

Exocrine vs. endocrine glands

Exocrine: release onto surfaces Endocrine: secrete into body fluids

Name for glands that release their fluids by exocytosis. Examples?

Merocrine (eccrine).

• Salivary glands

• Sweat glands of the skin

• Pancreatic glands

Glands that pinch off portions of the cell as part of the secretion. Example?

Apocrine glands.

• Mammary glands

Whole cells filled with secretion are released. Example?

Holocrine glands

• Sebaceous glands of the skin

What is the most wide-ranging and abundant type of tissue in the body?

Connective tissue

Functions of connective tissue

Mechanical binding and support, circulation of body fluids, insulation, storage of food reserves, inflammation

What are the 3 structural features that all connective tissues have in common?

• Cells

• Protein fibres

• Ground substance

Fibres and ground substance together form the:

Extracellular matrix of connective tissues

Is cartilage vascular or avascular?

Avascular

Types of connective tissue proper

• Areolar (loose) connective tissue

• Adipose connective tissue

• Reticular connective tissue

• Dense regular connective tissue

What are the 2 supporting connective tissues?

• Cartilage

• Bone

True or False: The consistency of the ground substance does not vary

False. It varies from fluid, to gel, to solid.

What are components of the ground substance?

• Glycosaminoglycans (GAG) such as sulphate and hyaluronic acid.

• Proteoglycan

• Adhesive glycoproteins

Cell names ending in “-blast” are (mature/immature)

Immature

Cell names ending in “cyte” are (mature/immature)

Mature

Roles of immature cells (blasts)

Secrete matrix and are actively mitotic

Roles of mature cells (cytes)

Maintaining the matrix. Are less active

What are the 3 types of fibres of connective tissue?

• Collagen

• Elastic

• Reticular fibres

Fibroblast

Actively mitosis cell that secreted ground substance and fibers

Mast cell

Has coarse, dark-staining granules (in the cytoplasm). Secrete heparin and histamine

Macrophages

Large and irregularly shaped phagocytize cells. Arise from monocytes (type of white blood cell). Wander through connective tissue where they engulf and destroy bacteria, foreign particles, and dead/dying body cells.

Heparin

A chemical that inhibits blood clotting

Histamine

A chemical that increases blood flow by dilating blood vessels

What does reticular connective tissue form?

Internal framework of the spleen, liver, bone marrow, and lymph nodes. Also closely associated with blood vessels and nerves

What do cells in reticular connective tissue contain?

• Fibroblasts (reticular cells)

• White blood cells

• Macrophages

Characteristics of reticular fibres

Short, thin branched network of collagen-like fibres

What characterizes an adipose cell/adipocyte?

A large internal lipid droplet which displaces the nucleus to the edge of the cell

What are dense connective tissues characterized by?

An abundance of fibers

2 types of dense connective tissue

• Regular

• Irregular

What sets apart dense irregular tissue from dense regular?

They have the same structural components, but dense irregular’s bundles of collagen fibers are much thicker and run in several directions

Where is dense regular connective tissue found?

In the skin dermis. Forms fibrous coverings around organs such as kidney, muscles, bones, and nerves.

3 types of cartilage found on the human body

• Hyaline cartilage

• Elastic cartilage

• Fibrocartilage

Most types of cartilage are surrounded by a layer of:

Perichondrium

What is perichondrium?

Dense connective tissue.

What is the most common type of cartilage?

Hyaline cartilage

Most of the embryonic skeleton is formed of:

Hyaline cartilage

Where are collagen fibers in the cartilage embedded?

In the gel-like matrix

Where is hyaline cartilage found in an adult human?

• Articular surfaces of bones

• Ends of the ribs

• Part of the nasal septum

• Larynx

• Trachea

• Bronchi

Compare fibrocartilage to other cartilage types

Fibrocartilage is less organized than other cartilage types, and it lacks a perichondrium

Characteristics of fibrocartilage

It provides strong support and can withstand heavy pressure. It forms pads, the vertebral discs between the individual vertebrae and the knee menisci between the tibia and femur. Also forms pubic symphysis (the joint between the pubic bones of the pelvis)

Function of bones

Support and protection. Provide cavities for fat storage and synthesis of blood cells. Storehouse for the minerals, calcium, and phosphorus required for various functions.

What are the two basic types of bone?

• Spongy (cancellous)

• Compact

Cancellous vs. compact bone

Cancellous: Found internally (generally at expanded ends of bone known as trabeculae). Compact: External layer of the bone. Is thickest along the length of the bone.

The spaces between the spongy bone trabeculae are filled with:

Bone marrow

What does an osteon consist of?

Concentric rings of bone called lamellae around a central (Haversian) canal containing blood vessels and nerves

What is the name for mature bone cells?

Osteocytes

Where are osteocytes found?

In lacunae between lamellae

Is bone vascular or avascular?

Vascular (highly)

Periosteum

A connective tissue layer surrounding the bone

How do blood vessels located in the periosteum work?

They penetrate compact bone through transverse perforating (Volkmann) canals which connect to the central canals that run longitudinally through the bone.

What are canaliculi?

Networks of small canals that radiate from each lacunae

How do individual osteocytes obtain nutrients and remove wastes?

Via their cytoplasmic extensions that occupy canaliculi.

Acid removes inorganic salts from bone, which causes the bone to become soft (the bone is decalcified). What characteristics of bone are provided by inorganic salts?

Inorganic materials/salts determine the bone's density

Baking bones removes the organic constitutes from the bone, which causes the bone to become brittle. What characteristics of bone are provided by the organic materials?

Organic materials determine the bone's flexibility

What type of epithelium is found lining the urinary bladder?

Transitional epithelium

What type of epithelium is found lining the small intestine?

Simple columnar

What type of epithelium is found lining the trachea?

Pseudostratified

What type of epithelium is found forming the epidermis of the skin?

Keratinized stratified squamous epithelium

What type of epithelium is found forming the blood capillaries?

Simple squamous

What kind of epithelium is best designed for: Absorption

Cuboidal and columnar

What kind of epithelium is best designed for: Rapid diffusion

Simple squamous

What kind of epithelium is best designed for: Protection

Stratified squamous

What type of connective tissue forms the framework of the liver, spleen, and lymph nodes?

Reticular connective tissue

What type of connective tissue fills in the spaces between organs and holds them in place?

Areolar (loose) connective tissue

What type of connective tissue composes tendons and ligaments?

Dense regular connective tissue

What connects muscle to bone?

Tendons

What connects bone to bone?

Ligaments

Why is bone a much thicker tissue than cartilage?

Bone is vascular and can continue to grow larger and larger. Cartilage is avascular and only has a "set" size to grow until. It receives its nutrients from diffusion which is not enough to grow extremely large.