Histology

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