1. Structures of the body

- CELLS→TISSUE→ORGAN

- over 200 types of cells (cytology = the study of cells)

- Organ- discrete structure composed of more than one tissue, with a specific function in the body (heart, skin, liver, kidney, brain)

2. Histology (the study of tissues)

- Tissue- group of cells with the same structure and common structure(s)

- A tissue is a mixture of:

1) Ground substance

2) Cells

3) Fibers

3. Tissue types

- Muscle Tissue

- Nervous Tissue

- Epithelium

- Connective Tissue

4. Muscle Tissue (detailed study later)

- contracts to cause movement

A. Skeletal- muscles attached to bones

B. Cardiac- muscles of heart

C. Smooth- muscles of walls of hollow organs

5. Nervous Tissue (detailed study later)

- internal communication (monitors and regulates the functions of the body

- consists of nerve cells (neurons) and glial cells

- Neurons are highly specialized nerve cells that generate and conduct nerve impulses

- Glial cells (supporting cells) are nonconducting cells that support, insulate and protect the delicate neurons

- Nervous tissue is found in:

• Brain

• Spinal cord

• Nerves

6. Epithelial Tissue (Epithelium)

- A sheet of cells that covers a body surface or lines a cavity

• Covering and lining epithelium- forms the outer layer of the shin; lines the open cavities of the urogenital, digestive and respiratory systems; covers the walls and organs of the closed ventral body cavity

• Glandular epithelium- fashions the glands of the body

A. General characteristics

-closely aggregated cells

-hardly any intercellular ground substance

-supported by a basal lamina = basement membrane

-covers the body (epidermis of the skin)

-forms the lining (''surface layer'') of internal cavities- intestines, airways, blood vessels, bladder, etc.

-main component of glands

-has high regenerative capacity

-does not contain blood vessels (avascular), but is supplied by nerve fibers (innervated)

B. Basement membrane

-all epithelial sheets rest upon and are supported by connective tissue

-the basement membrane keeps cells stick to the connective tissue

• Basal lamina (collagen fibers + glycoproteins)

• Reticular lamina (reticular fibers)- layer of extracellular material containing a network of collagen protein fibers

C. Classification

a. First name (number of cells) + second (shape of cells)

• Squamous cells- flattened and scalelike

• Cuboidal cells- boxlike and approximately as tall as they are wide

• Columnar cells- tall and colum shaped (cylindrical)

b. Based on cell layers

• Simple epithelia- consists of a single cell layer (typically found where secretion, absorption and filtration occur)

• Stratified/Special epithelia- composed of two or more cell layers stacked on top of each other (common in high-abrasion areas where protection is important)

-ex: airways- epithelium with ''cilia'' (hairs) for mucus transport

D. Functions

- Covering surfaces (internal and external)

- Absorption (ex: intestines/bowels)

- Filtration (blood vessels, alveolar air-sacks)

- Secretion (ex: glands)

- Moving mucus- respiratory epithelium

- Excretion

- Protection

- Sensory reception (skin: pain, touch, temperature, etc.)

7. Connective Tissue

-tissues that give support to the body (shape) and help to connect several tissues, organs or body parts

-most abundant and widely distributed of the primary tissues

A. Structure Elements

-three main elements: ground substance, fibers and cells

a. Ground Substance- the unstructured material that fills the space between cells and contains the fibers

-composed of adhesion proteins, interstitial (tissue) fluid and proteoglycans

b. Fibers- structures that provide support

• Collagen Fibers

-constructed primarily of collagen

-collagen molecules → cross-linked fibrils → thick fibers

-extremely tough and provide high tensile strength

• Elastic Fibers

-long thin fibers that form branching networks in the extracellular matrix

-contain the protein elastin (stretch and recoil)

-found where greater elasticity is needed (ex: skin, lungs…)

-shape → (Cutis-dermis)

• Reticular Fibers

-short, fine, collagenous fibers

-form delicate networks that surround small blood vessels and support the soft tissue of organs

-found in the basement membrane of the epithelium and around capillaries

-abundant where connective tissue abuts other tissue types

c. Cells

-each major class has a resident cell type that exists in immature (undifferentiated) and mature forms

• Immature cells- indicated by the suffix ''blast''

• Mature cells (less active mode)- suffix ''cyte''

-the connective tissue is home to other cell types: fat cells, white blood cells, mast cells, macrophages

B. Types of Connective Tissue

a. Connective Tissue Proper

• Loose Connective Tissue

-open maze structure that fills the spaces between organs

-supports epithelial tissue (subcutaneous tissue: airways: intestines…)

-contains→ fibers (collagen, elastic, some reticular)

→ cells- fibrocytes (at rest), fibroblasts (growth and repair), microphages (remove damaged parts), mast cells

→blood vessels and nerves

• Dense Connective Tissue

-contains → mainly collagen fibers

→ some fibroblasts and fibrocytes

◊ Regular dense tissue- tendons, ligaments, aponeuroses

◊ Irregular dense tissue- dermis, fibrous capsules of organs and of joints

◊ Elastic dense tissue- walls of large arteries, walls of bronchial tubes…

b. Cartilage

-stands up to both tension and compression (it is tough but flexible)

-lacks nerve fibers and is avascular

• Hyaline Cartilage (gristle)

-most abundant cartilage

-contains a lot of collagen fibers, but the matrix appears glassy

-covers joint surfaces (helps to move the joints smoothly and helps to relieve pressure in the joints)

-supports the tip of the nose, connects the ribs to the sternum, rib 1 cartilage, supports most respiratory system passages

• Fibrocartilage

-intermediate between hyaline cartilage and dense regular connective tissues

-has rows of chondrocytes and rows of thick collagen fibers

-found in intervertebral discs, pubic symphysis (pelvis), discs of knee joint (meniscus)

• Elastic Cartilage

-identical to hyaline cartilage, but has many more elastic fibers

-found in the external ear (pinna) and epiglottis

c. Bone (Osseous Tissue)

-ability to protect and support body structures

-bones provide cavities for storing fat and synthetizing blood cells

-hard and rigid bone matrix → collagen fibers and inorganic calcium salts (bone salts)

-contains and is well supplied by invading blood vessels

-cells- osteoblasts and osteocytes

-structural units - osteons

-cortex and trabecular bone- cancellous: spongy bone

d. Blood

-the fluid within blood vessels

-most atypical connective tissue- does not connect things or give mechanical support

-consists of blood cells, surrounded by a nonliving fluid matrix (blood plasma)

-cells → majority of red blood cells (erythrocytes)

→ white blood cells (leukocytes)

→platelets

-it is a transport vehicle for the CV system; carries nutrients, wastes, respiratory gases and other substances