Epithelial and Connective Tissue Classifications

Simple squamous

1 layer, flat cells

Located in lung alveoli, eye, and lining of body cavities and blood vessels

Endothelium

Simple squamous; lines blood and lymphatic vessels

Endocardium

Simple squamous; lines ventricles and atria of heart

Mesothelium

Simple squamous; lines walls and closed body cavities (e.g. abdominal, pericardial, or pleural cavities)

Stratified squamous

Many layers, flat

Keratinized makes up skin surface

Nonkeratinized is moist and located in oral cavity, pharynx, esophagus, anus, and vagina

Simple cuboidal

1 layer, cube-shaped

Lines exocrine ducts and glands, located in portion of kidney

Stratified cuboidal

Many layers, cube-shaped, RARE

Located in sweat and mammary glands

Simple columnar

1-layer, rectangular

Located in stomach, intestines, uterine tubes, and kidney ducts

For mucus secretion

Stratified columnar

Many layers, rectangular

Located in pharynx, epiglottis, salivary gland ducts, and urethra

Pseudostratified columnar

One layer with staggered nuclei, ciliated, rectangular

Located in nasal cavity, trachea, and larger lung airways

Transitional

Stratified with large, round apical cells

Located in bladder

Areolar tissue

Loose connective tissue proper

Function: Wraps and cushions joints and allows for independent movement

Location: between muscles, dermis

Ground substance/fibers: Gel-like with collagen, elastic, and reticular fibers

Cell types: fibroblasts, immune cells (mast cells), adipocytes

Adipose tissue

Loose connective tissue proper

Function: acts as energy storage, provides insulation and cushioning, hormone secretion

Location: fat deposits throughout body

Ground substance/fibers: gel-like and minimal ground substance; reticular and collagen fibers

Cell types: adipocytes, fibroblasts

Reticular tissue

Loose connective tissue proper

Function: prevents distortion of soft organs

Location: around liver, kidneys, spleen, lymph nodes, bone marrow

Ground substance/fibers: gel-like with a high number of reticular fibers that form a “stroma”

Cell types: reticular predominantly, fibroblasts, adipocytes, immune cells

Dense regular tissue

Dense connective tissue proper

Function: withstand tensile stress in one direction

Location: tendons, ligaments, aponeuroses

Ground substance/fibers: gel-like minimal ground substance due to high number of fibers; parallel collagen fibers

Cell types: fibroblasts, immune cells

Dense irregular tissue

Dense connective tissue proper

Function: withstand tensile stress in many directions

Location: joint capsules, covers organs and bones, in dermis

Ground substance/fibers: gel-like minimal ground substance due to high number of fibers; irregular arrangement of collagen fibers

Cell types: fibroblasts, immune cells

Elastic tissue

Dense connective tissue proper

Has more elastic fiber than collagen so it is springy and resilient

Located between vertebrae, large blood vessel walls, bronchial tubes, and the penis

Blood

Fluid connective tissue

Function: bring oxygen and nutrients to cells

Location: CV system vessels

Ground substance/fibers: fluid plasma, no fibers

Cell types: Erythrocytes (RBC), Leukocytes (WBC), platelets

Lymph

Fluid connective tissue

Function: lymph is screened by immune system for infection and returned to CV system

Location: lymphatic vessels

Ground substance/fibers: fluid, no fibers

Cartilage

Supporting connective tissue

Avascular and separated from other tissue via perichondrium; categorized by number of extracellular fibers; very low regenerative capacity

Hyaline cartilage

Most common type of cartilage

Function: reduce friction at joints

Location: articular cartilage covers ends of bones at joint (ex. knee, shoulder, elbow)

Ground substance/fibers: semi-solid with collagen and elastic fibers

Cell types: chondrocytes, chondroblasts in lacunae, fibroblasts

Elastic cartilage

Function: offers support and retains shape

Location: outer ear, epiglottis

Ground substance/fibers: semi-solid with elastic and collagen fibers

Cell types: chondrocytes in lacunae

Fibrocartilage

Function: resists compression and cushions bones

Location: between vertebrae, pubic bones

Ground substance/fibers: semi-solid with interwoven collagen fibers

Cell types: chondrocytes in lacunae

Bone

Supporting connective tissue

Function: makes bones both strong and flexible due to unique composition

Location: bones

Ground substance/fibers: solid matrix made of calcium carbonate, calcium phosphate, and collagen fibers

Cell types: osteoblasts, osetocytes, osteoclasts

Stratum spinosum

-2nd deepest layer

-Keratinocytes held together by desmosomes

Stratum corneum

-Most superficial layer

-Contains dead cells

-Cells are filled with keratin, and glycolipids are in the extracellular space

Stratum lucidum

-Only found in thick skin

-2nd most superficial layer in thick skin

Stratum granulosum

-2nd most superficial layer in thin skin, 3rd most superficial in thick skin

-Cytoplasm contains lamellated and keratohyalin granules

-Organelles are deteriorating and cells begin to flatten

Stratum basale

-Deepest layer, connected to basement membrane by hemidesmosomes

-Contains mitotic stem cells

-Contains melanocytes and dendritic cells