Histology

How many cells have a nucleus?

How many cells have a nucleus?

less than 75%

Cells that connect body parts or cover/line organs

• erythrocytes

• fibroblasts

• epithelial cells

Cells that move organs and body parts

• skeletal muscle cell

• smooth muscle cell

Cell that stores nutrients

fat cell

Cells that fight disease

Monocytes

Cell that gathers information and controls body functions

Nerve cell

Cells of reproduction

• sperm

• ovary

Tissue

• group of cells that work together to perform a specific function

Histology

• study of tissues

Epithelial Tissue

• lines walls of open tubes, body surfaces and all body cavities

• lines the vessels of the secretory system and digestive system

• provides secretory and absorptive surfaces

• possess little to no extracellular matrix

• avascula

Functions of Epithelial Tissue

• physical protection as a barrier

• reduces dehydration and abrasion

• protects from physical, chemical and biological agents

• absorption, regulating the passage of certain molecules in out of the body

• secretion of sweat or oil or digestive enzymes

• have nerve endings that can detect various sensations

Main Characteristics of Epithelial Cells

• tightly packed to ensure a barrier and absorptive/secretive functions

• organized assembly of apical, basal and lateral surfaces

• exhibits polarity which is necessary for selective movement of molecules

• highly regenerative to repair damage at a rapid rate

Apical Surface

• top of epithelial cells that faces the body surface, body cavity, lumen of the internal organ or duct

Lateral Surface

• part of epithelial cells that contains junctions to communicate with other cells

Basal Surface

• apart of the epithelial cells that adheres to the basement membrane

Basement Membrane

• made of 2 different layers from different cells the basal lamina and reticular lamina

• supports epithelial cells

• provides surface for cell movement

• restricts the passage of substances between epithelial and connective tissue

Reticular Lamina

• bottom layer of the basement membrane

• formed by cells in connective tissue

Basal Lamina

• upper layer of the basement membrane

• formed by epithelial cells

Covering Epithelia

• cells arranged in layers that cover external surfaces or line the cavities of the body

• characterized by the number of cells layers that make up the tissue and the cell shape

Single Epithelium

• single layer of cells with all cells attached to the basement membrane

Stratified Epithelium

• two or more layers of cells

• only the bottom layer is attached to the basement membrane

Pseudostratified Epithelium

• single layer but not all cells reach the apical surface

• nuclei looks like multiple layers but there is only one

Squamous Epithelium

• flattened egg shape

• flat nuclei

Cuboidal Epithelium

-about the same size on all sides

• nucleus is centrally located

• round nuclei

Columnar Epithelium

• cells are taller than they are wide

• nucleus is oval and located in the basal region

Simple Squamous Epithelium

• single layer of flat disc-like cells with a flattened nuclei

• surface for filtration and diffusion

• found in alveoli, glomeruli nephrons, blood vessel and capillary lumens, body cavity linings

Simple Cuboidal Epithelium

• single layer of cube-like cells with large, round nuclei

• responsible for secretion and absorption

• found in ducts and glands, kidney tubules, ovary and thyroid

Simple Columnar Epithelium

• single layer of tall rectangular cells with an elongated nuclei

• microvilli and cilia common on apical surface

• for absorption and secretion

• mainly in the lining of the digestive and respiratory tract

Pseudostratified Columnar Epithelium

• single layer of columnar cells of different heights and nuclei

• for secretion and propulsion and may be ciliated

• found in large glands, the male sperm duct and the respiratory tract (mainly the trachea)

Stratified Squamous Epithelium

• multiple layers of squamous cells on a basement membrane

• basal cells are cube/columnar shaped and mitotically active

• form protection against abrasion and damage for tissue underneath

• cells change shape from upper (flatter squamous) to lower layers

• found in all the places you can put a dick (includes esophagus)

Stratified Cuboidal/Columnar Epithelium

• two or more layers of cuboidal or columnar cells

• used for secretion

• found in male sperm duct, sweat and mammary glands, pharynx and male urethra

Transitional Epithelium

• appears to be stratified squamous cuboidal

• surface cells are rounded/squamous

• allow for stretch

• lines the urinary tracts including the ureter, bladder and urethra

Glandular Epithelia

• cells specialized for secretion production

• glands consist of one or more cells that secrete specific products (water, lipids or steroids)

• classified by the cell number (unicellular or multicellular) and where the product is released (endocrine or exocrine)

Exocrine Glands

• cells that secrete their products into ducts

• lead to a body surface or body cavity

Unicellular Exocrine Gland

• only have one goblet cell that secretes mucous

• found in the lining of the digestive tract to reduce friction in the esophagus and large intestine

Multicellular Exocrine Glands

• divided into the duct region and secretory region

• usually have connective tissue, nerves, blood vessels around the outside

• produces substances and forms tubules for transport

Multicellular Gland Classification

• simple (unbranched) or compound (branched)

• tubular (tublike), acrinar/alveolar (flasklike) or both

Development of Exocrine Glands

• maintain its connection with the surface through ducts

Endocrine Glands

• do not have ducts and secrete directly into the extracellular space or blood vessel

• travels to specific targets

• cells of the adrenal gland secrete products directly into blood vessels

• cells of the thymus gland secrete into spaces between cells

Development of Endocrine Glands

• epithelium loses its ducts and secrete products directly into blood vessels

Connective Tissue

• provides support or integrity for other tissues/organs

• most diverse abundant, widely distributed and structurally varied

• connects one structure to another structure

• includes tendons ligaments body fat, bones, blood and cartilage

Functions of Connective Tissue

• protection of tissues and organs against unnecessary movement

• physical support (muscle attachments with bones)\

• energy storage/insulation (adipose tissue)

• transports substances (blood)

Ground Substance of Connective Tissue

• interstitial fluid that mixes with fibers to make up the extracellular matrix

• a mixture of proteins to provide structural support along with carbohydrates

• nutrients and other substances can pass between cells and blood vessels

Fibers

• 3 different kinds that provide support for connective tissue

• may help determine structural properties of tissue

Collagen

• most common and strongest fiber

• can resist being pulled apart

Elastic

• fiber that can stretch and return to its original shape/length

Reticular

• thin, branching collagen fibers that form extensive networks

Cells in Connective Tissue

• have active and less active states

• developing are specific cell blasts

• maturing are specific cell cytes

Osteoblasts

• actively lay down minerals

Osteocytes

• living but not active in the matrix

Fibroblasts

• very common cell of connective tissue

• have secrete fibers

Macrophages

• cleanup cells that engulf bacteria and cellular debris

Plasma Cells

• secrete antibodies

• associated with the immune system

Mast Cells

• abundant by blood vessels

• produced histamine that are involved in the inflammatory response

Adipocytes

• cells of fat storage

White Blood Cells

• not normally present but migrate in response to infections

Areolar Loose Connective Tissue

• most common, found under epithelial layers and surrounding organs

• loosely-packed assembly of all fiber types and immune cells

• cushions organs and contains key immune mediators to fight off infections

Adipose Loose Connective Tissue

• matrix surrounded by tightly packed adipocytes

• insulates and protects organs while providing energy storage

• found around organs and within the subcutaneous layer of skin

Reticular Loose Connective Tissue

• network of reticular fibers that are loosely organized

• forms a flexible meshwork

• supports tissues and immune cells

• found in lymph nodes, bone marrow and splenic pulp

Regular Dense Connective Tissue

• fibroblasts embedded within a regularly parallel ordered assembly of collagen fibers

• resists pulling from stress

• attaches muscle to bone (tendons)

• attaches bone to bone (ligaments)

Irregular Dense Connective Tissue

• irregularly arranged collagen fibers with fibroblasts embedded within

• resists force from multiple directions

• found in the dermis, joint capsules and underlying epithelial linings including the digestive tract

Elastic Dense Connective Tissue

• dense regular connective tissue enriched with ordered arrangements of elastin fiber

• allows for stretch and recoil of tissue

• important in blood and air

• found in the walls of arteries and bronchial tubes and in some ligaments

Cartilage

• collagen and elastic fibers in a specialized matrix -provide support and withstand deformation

• 3 types

Chrondrocytes

• mature cells found in lacunae that are responsible for cartilage formation

Hyaline Cartilage

• most abundant and the weakest

• found in developing bones

Fibrocartilage

• strongest and has lots of collagen

• found in intervertebral discs

Elastic Cartilage

• contains lots of elastin to maintain shape

• found in the ears

Bone

• similar to cartilage but has a solid matrix

• osteocytes are formed in lacunae

Blood

• matrix of mostly water

• has red and white blood cells ad platelets

Lymph

• matrix similar to blood with fewer proteins

• cellular composition varies

Muscle Tissue

• generates mechanical force

• three kinds

Nervous Tissue

• glial cells provide protection, nourishment and support to nerve cells

• provide long-distance communication within the body

• conducts the electrical impulses

Epithelial Membranes

• have both epithelial and connective tissue

Synovial Membranes

• only have connective tissue

Cutaneous Membrane

• type of epithelial membrane that covers the body (is skin)

• keratinized, stratified squamous epithelium attached to a thick layer of connective tissue

• exposed to air and dry

Mucous Membranes

• type of epithelial membrane that lines the passageways that open to the body surface

• very important in defense by trapping particles and lubricates passages

• may contain antibacterial agents

• lines the digestive, respiratory and reproductive tracts

Serous Membranes

• type of epithelial membrane that lines the body cavity, not opening to the exterior

• parietal layer is attached to the cavity

• visceral layer is attached to the organs

Synovial Membranes

• where 2 bones come together

• consists of connective tissue only

• cells secrete synovial fluid that acts as a lubricant