Unit 3: Histology Anatomy and Physiology PART 2: Connective Tissue

Histology Histology is defined as the study of the microanatomy of animal and plant tissues A tissue is a group of like cells of similar specialized structure which carry out similar specific functions.

4 types of tissues A tissue is a group of like cells of similar specialized structure which carry out specific functions. Groups of tissues compose and work together to form organs. All organs are composed of two or more types of tissues. There are four major tissue types: Epithelial Connective Muscle Nervous

2. Connective Tissue

2. Connective Tissue A. Locations Found everywhere in the body Includes the most abundant and widely distributed tissues

2. Connective Tissue B. Functions Binds body tissues together Supports the body Provides protection

2. Connective tissues: C. Characteristics Connective tissues get their name because they attach or hold different tissue types together. Produce materials which they secrete in their extracellular space to form the extracellular matrix Extracellular matrix: Non-living material that surrounds living cells

2. Connective tissues: C. Characteristics Often the cells are very scattered about and few in number. This is why some connective tissues take long periods of time to heal when damaged (cartilage and bone). Variations in blood supply Some tissue types are well vascularized Some have a poor blood supply or are avascular

2. Connective tissues: C. Characteristics The matrix varies depending on the connective tissue type. Bones: are hard, solid, crystalline structure Cartilages: flexible Tendons and ligaments: composed of protein fibers Dermis of skin: sponge-like rich in Adipose: soft Plasma of blood: liquid

D. Examples of Connective Tissue

2. Connective tissues: D. Examples Loose irregular connective tissue Loose reticular connective tissue Adipose tissue Dense regular connective tissue Dense irregular connective tissue Hyaline cartilage Elastic cartilage Fibrocartilage Bone Blood

2. Connective tissues: Examples I. Loose Irregular Name: Loose irregular connective Structure: Areolar tissue has a gel like matrix with cells called fibroblasts Fibroblasts: produce two types of protein fibers, collagen (larger) and elastin (small thread-like). Areolar: Soft, pliable tissue like “cobwebs”

2. Connective tissues: Examples I. Loose Irregular Location: Most widely distributed connective tissue Around the organs, under mucus membrane epithelial and surrounding capillaries.

2. Connective tissues: Examples I. Loose Irregular Functions: Functions as a packing tissue Holds and conveys tissue fluid. Can soak up excess fluid (causes edema)

2. Connective tissues: Examples I. Loose Irregular

2. Connective tissues: Examples I. Loose Irregular Mucosa epithelium Lamina propria Elastic fibers Collagen fibers Fibers of matrix Fibroblast nuclei Nuclei of fibroblasts (e) Diagram: Areolar Photomicrograph: Areolar connective tissue, a soft packaging tissue of the body (300×). Figure 3.19e

2. Connective tissues: Examples ii. Loose Reticular Name: Loose reticular connective tissue Structure: Has a network of collagen reticular fibers, which have a netted arrangement. Location: This tissue composes the spleen, the lymph nodes, and the bone marrow.

2. Connective tissues: Examples ii. Loose Reticular Function: These fibers form a soft internal skeleton (stroma) that supports other cell types, Particularly erythrocytes (red blood cells) and leukocytes (white blood cells

2. Connective tissues: Examples ii. Loose Reticular Spleen White blood cell (lymphocyte) Reticular cell Reticular fibers Blood cell Reticular fibers (g) Diagram: Reticular Photomicrograph: Dark-staining network of reticular connective tissue (430×). Figure 3.19g

2. Connective tissues: Examples ii. Loose Reticular

2. Connective tissues: Examples iiI. Adipose Tissue Name: Adipose tissue Location: under the skin, around the kidneys, heart, within the abdomen, and breasts of females

Connective Tissues Types Adipose Tissue Distribution

2. Connective tissues: Examples iiI. Adipose Tissue Structure: Matrix is an areolar tissue composed of collagen and elastin fibers Adipocytes (fat cells) are present: large cells with their nuclei pushed to the side by large lipid (fat) deposits Functions: Insulates the body Protects some organs Serves as a site of fuel storage

2. Connective tissues: Examples iiI. Adipose Tissue Nuclei of fat cells Vacuole containing fat droplet Nuclei of fat cells Vacuole containing fat droplet (f) Diagram: Adipose Photomicrograph: Adipose tissue from the subcutaneous layer beneath the skin (430×). Figure 3.19f

2. Connective tissues: Examples iV. Dense Regular Name: Dense regular connective tissue (dense fibrous tissue) Structure: Main matrix element is collagen fibers tightly packed together. Some elastin fibers are present. Fibroblast (cells that make fibers) are present

2. Connective tissues: Examples iV. Dense Regular Locations: Tendons—attach skeletal muscle to bone Ligaments—attach bone to bone at joints Dermis—lower layers of the skin

2. Connective tissues: Examples iV. Dense Regular

2. Connective tissues: Examples iV. Dense Regular Functions: Can withstand great pulling force when it is applied in one direction. Attaches muscles to bone or muscles to muscles.

2. Connective tissues: Examples iV. Dense Regular Ligament Tendon Collagen fibers Collagen fibers Nuclei of fibroblasts Nuclei of fibroblasts (d) Diagram: Dense fibrous Photomicrograph: Dense fibrous connective tissue from a tendon (500×). Figure 3.19d

Video Clip Dense Regular: 2:22 https://www.youtube.com/watch?v=y_mjSk5 TE1E

2. Connective tissues: Examples V. Dense Irregular Name: Dense irregular connective Structure: Matrix is primarily composed of collagen and elastin fibers irregularly arranged (not parallel). Fibroblast are the cells present and produce the matrix

2. Connective tissues: Examples V. Dense Irregular Location: in the dermis of the skin, the submucosa of the digestive tract and the fibrous capsules surrounding certain joints and organs. Function: This tissue is able to withstand tension or stress exerted in many directions. Also provides structural strength.

2. Connective tissues: Examples V. Dense Irregular

2. Connective tissues: Examples VI. Cartilage Cartilage General Structure: Cartilage is a connective tissue which has qualities between dense connective tissue and bone. Cells called chondroblasts secrete the matrix. When the cells mature they are trapped within cavities called lacunae. These mature cells surrounded by matrix are called chondrocytes Avascular and lacks nerve fibers

2. Connective tissues: Examples VI. Cartilage There are three types of cartilages and they differ in the composition of their matrix: Hyaline cartilage Elastic cartilage Fibrocartilage

2. Connective tissues: Examples VI. Hyaline Cartilage Name: Hyaline cartilage (most common type of cartilage in body) Structure: The matrix is amorphous (without any particular shape) and rubbery Has a network of collagen fibers present that are not visible. It appears bluish white and glassy (semi- translucent)

2. Connective tissues: Examples VI. Hyaline Cartilage Location: At the end of long bones Forms the cartilages of the rib cage, nose, trachea, and larynx (Adam’s apple) Entire fetal skeleton prior to birth Function: Support, reinforcement, cushioning, and resistance to compressive stress

2. Connective tissues: Examples VI. Hyaline Cartilage In a young child the majority of the appendicular skeleton is composed of this type of cartilage which is eventually replaced by bone tissue as the child matures.

2. Connective tissues: Examples VI. Hyaline Cartilage

Chondrocyte (Cartilage cell) Chondrocyte in lacuna Lacunae Matrix (b) Diagram: Hyaline cartilage Photomicrograph: Hyaline cartilage from the trachea (500×). Figure 3.19b

2. Connective tissues: Examples VII. Elastic Cartilage Name: Elastic cartilage Structure: The matrix is similar to hyaline cartilage – amorphous with collagen fibers BUT the matrix is rich in elastin fibers which are visible and usually stain dark purple. Location: It is located in the pinna (outer ear) and the epiglottis of the throat. Function: This cartilage maintains the shape of a structure while allowing great flexibility.

2. Connective tissues: Examples VII. Elastic Cartilage

2. Connective tissues: Examples VIII. Fibrocartilage Name: Fibrocartilage Structure: The matrix of this cartilage is less firm than that of hyaline cartilage has many thick, visible collagen fibers present Location: intervertebral discs, the knee and the pubic symphysis. Function: the absorption of compressive shock

2. Connective tissues: Examples VIII. Fibrocartilage

2. Connective tissues: Examples VIII. Fibrocartilage Chondrocytes in lacunae Chondro- cites in lacunae Collagen fiber Collagen fibers (c) Diagram: Fibrocartilage Photomicrograph: Fibrocartilage of an intervertebral disc (110×). Figure 3.19c

Cartilage Video Clips Hyaline Cartilage: 4:27 https://www.youtube.com/watch?v=PVoz28_ n0uU Elastic Cartilage: 1:58 https://www.youtube.com/watch?v=1rgtmJN Lwn0 Fibrocartilage: 1:48 https://www.youtube.com/watch?v=imDyTw vgNaQ

2. Connective tissues: Examples IX. Osseous Tissue Name: Bone or Osseous tissue Structure: Bone tissue matrix is secreted by cells called osteoblasts. The matrix is composed of collagen fibers and calcium (hydroxyapeptite crystals). The bone matrix is constantly being broken and reabsorbed by cells called osteoclasts.

2. Connective tissues: Examples IX. Osseous Tissue Structure (cont’d): The cells which are in the lacunae and surrounded by the matrix are called osteocytes. The bone tissue is highly vascularized and has nerve fibers present. The blood vessels and nerve supply are located in tunnel-like structures which run through the matrix called Harversian Canals.

Bone cells in lacunae Central canal Lacunae Lamella (a) Diagram: Bone Photomicrograph: Cross-sectional view of ground bone (300×). Figure 3.19a

2. Connective tissues: Examples IX. Osseous Tissue Function: Support, protection, Provides levers to which muscles act on to produce movement, Storage of calcium, phosphorous, and other mineral The marrow inside the bone is the site of blood cell production

2. Connective tissues: Examples IX. Osseous Tissue

2. Connective tissues: Examples X. Blood Name: Blood Function: transport of nutrients and the removal of waste from the body’s tissues Structure: Blood is composed of formed elements (cells) suspended in a fluid matrix called plasma. Fibers are visible during clotting

2. Connective tissues: Examples X. Blood

2. Connective tissues: Examples X. Blood Structure (cont’d): There are three types of formed elements, each with a specific function. Erythrocytes or red blood cells function in the transport of oxygen. Leukocytes or white blood cells are involved with our body’s defense against infection. Thrombocytes or platelets are actually fragments of cells which are involved in blood clot formation to prevent blood loss.

2. Connective tissues: Examples X. Blood Blood cells in capillary Neutrophil (white blood cell) White blood cell Red blood cells Monocyte (white blood cell) Red blood cells (h) Diagram: Blood Photomicrograph: Smear of human blood (1300×) Figure 3.19h

Video Clips Blood Smear: 6:10 https://www.youtube.com/watch?v=jJqHdwg FH3c