Anatomy and Histology: Types, Functions, and Locations of Tissues

Epithelium

All four tissue types are derived from differentiated stem cells that have various parts of their genetic code either active or inactive.

Epithelial Tissue Characteristics

Attached to underlying connective tissue by basement membrane. Covers all body surfaces, inside and outside. Primary glandular tissue. Poorly vascularized. Reproduce rapidly.

Epithelial Tissue Function

Protection, Secretion, Absorption, Excretion, Sensory (pressure) perception.

Simple Squamous

Appearance- single-layered, flat. Function- diffusion, filtration. Location- alveoli (air sacs), capillary walls.

Simple Cuboidal

Appearance- single-layered, cube shaped. Function- absorption and secretion. Location- lining of kidney tubules, ducts of glands, surface of ovaries.

Simple Columnar

Appearance- single-layered, elongated with nuclei generally positioned at the same level in each cell. Contain goblet cells that secrete mucous. Function- absorption, protection, secretion. Location- line the digestive tract, can form microvilli, in females- lining of uterus and Fallopian tubes (ciliated).

Pseudostratified (Ciliated Columnar)

Appearance- appear layered, but actually, a single layer of cells with nuclei displaced at various levels. Almost always ciliated. Also, contain goblet cells. Function- cilia-aided movement, secretion. Location- line the trachea and male reproductive tubes.

Stratified Squamous

Appearance- multi-layered, flat cells. Thick keratinized or unkeratinized forms. Function- protection. Location- epidermis is keratinized while cheek cells and lining of esophagus are non-keratinized.

Transitional Epithelium

Appearance- multi-layered, containing both cube-shaped and flat cells. Function- capable of stretching. Form barrier to block or prevent diffusion from occurring. Location- lines the urinary bladder and urethra.

Connective Tissue Characteristics

Most common major type of tissue. Consists mostly of extracellular matrix or (ECM) made of fluids and fibers also known as ground substance. Generally has a good blood supply.

Connective Tissue Function

Connects, defends, supports, and transports.

Loose Areolar

Appearance- thick, gel-like with scattered cells and fibers. Function- found between many internal body organs and under the skin. Serves to support and protect these internal structures. Location- widespread throughout the body.

Adipose

Appearance- two types, 'white fat' for excess energy needs. 'brown fat' less abundant for generating body heat. Function- energy storage, protection, insulation. Location- widespread. In particular, surrounds vital organs such as heart and kidneys.

Dense Fibrous

Appearance- two types, regular and irregular, based on fiber arrangement. Function- Regular fibers provide tensile strength. Irregular fibers withstand forces in all directions.

Regular fibers

Found in tendons and ligaments.

Irregular fibers

Found in the dermis, spleen, and cortex of the kidney.

Reticular (Reticuloendothelial)

Forms a 'mesh' of reticulin to filter blood and lymph in assisting the immune system.

Appearance of Reticular fibers

Net-like swirling fibers with overlying cells.

Location of Reticular fibers

Liver, spleen, lymph nodes, bone marrow.

Hyaline Cartilage

Most common type of cartilage in the body, allows for smooth movement.

Appearance of Hyaline Cartilage

'Glass-like', slippery, fibers are present but difficult to observe under microscope.

Location of Hyaline Cartilage

Ends of long bones at the joints, tracheal rings, ball of nose, rib cartilages.

Elastic Cartilage

Most flexible form of cartilage, allows for movement and vibration.

Appearance of Elastic Cartilage

Contains many elastin (thin) fibers.

Location of Elastic Cartilage

External ear, larynx.

Fibrocartilage

Strongest and most durable cartilage, absorbs compressive forces.

Appearance of Fibrocartilage

Comprised of numerous collagen (thick) fibers.

Location of Fibrocartilage

Intervertebral disks, meniscus in knee, pubic symphysis.

Bone

Rigid structure that provides movement, protection, support, and blood formation in the marrow.

Appearance of Bone

Comprised of rigid, concentric cells (circular rings like a tree trunk).

Location of Bone

Widely distributed.

Blood

Transports nutrients and gases, provides defense and immunity, and aids in clotting.

Appearance of Blood

Three types of cells: erythrocytes, leukocytes, and platelets found throughout plasma.

Location of Blood

Widely distributed, circulates through the cardiovascular system.

Mesenchyme

Undifferentiated connective tissue cells, known as adult stem cells.

Appearance of Mesenchyme

Undifferentiated connective tissue cells.

Location of Mesenchyme

Bone marrow when forming.

Skeletal Muscle

Voluntary muscle that contracts and relaxes to move body parts.

Appearance of Skeletal Muscle

Striated, long non-branching fibers (cells), multi-nucleated.

Location of Skeletal Muscle

Widely distributed.

Smooth Muscle

Involuntary muscle involved in transportation and storage.

Appearance of Smooth Muscle

Spindle-shaped cells, nuclei typically shaped like a cigar.

Location of Smooth Muscle

Generally throughout the gastrointestinal tract, urinary bladder, and walls of arteries.

Cardiac Muscle

Involuntary muscle that transports blood throughout the circulatory system.

Appearance of Cardiac Muscle

Striated, branching fibers, single nucleus, intercalated disks.

Location of Cardiac Muscle

Heart.

Neuron

Nerve cell that receives and transmits electrical and/or chemical signals.

Appearance of Neuron

Nerve cell body, axons, dendrites.

Location of Neuron

Widespread.

Neuroglia (glial cells)

Support cells for neurons that lack axons and dendrites.

Appearance of Neuroglia

Much smaller than neurons.

Function of Neuroglia

Outnumber neurons 10:1 and provide support for neurons.

Location of Neuroglia

Widespread.