Chapter Histology Tissues and Membranes

Adipose Connective Tissue Mature cells are specialized for storage of triglycerides and largest cells in body. Mature cells are specialized for storage of triglycerides and largest cells in body. Adipocytes are derived from fibroblast cells. Adipocytes are derived from fibroblast cells. Cells fill up with triglycerides which push cell nuclei to the periphery of the cell. Cells fill up with triglycerides which push cell nuclei to the periphery of the cell. Most adipose in adults is white adipose tissue. Most adipose in adults is white adipose tissue. Brown adipose tissue gets its coloration from rich vascular supply and is less common. Brown adipose tissue gets its coloration from rich vascular supply and is less common. Functions as insulation, energy storage, protects and supports organs. Functions as insulation, energy storage, protects and supports organs. Usually found with or close to areolar tissue. Usually found with or close to areolar tissue.

Adipose Connective Tissue

Reticular Connective Tissue Composed of interlacing reticular fibers with various types of cells interspersed among the fibers. Composed of interlacing reticular fibers with various types of cells interspersed among the fibers. Forms the stroma of the liver, spleen and lymph nodes and helps to bind smooth muscle cells. Forms the stroma of the liver, spleen and lymph nodes and helps to bind smooth muscle cells.

Reticular Connective Tissue

Dense Regular Connective Tissue Composed of bundles of collagen fibers regularly arranged in parallel patterns. Composed of bundles of collagen fibers regularly arranged in parallel patterns. Fibroblasts are interspersed between the collagen fibers. Fibroblasts are interspersed between the collagen fibers. Main component in ligaments, tendons, aponeuroses and fascia. Main component in ligaments, tendons, aponeuroses and fascia. Has a wavy appearance on slides. Has a wavy appearance on slides. Forms tendons to attach muscles to bone and ligaments to attach bones to bones. Forms tendons to attach muscles to bone and ligaments to attach bones to bones.

Dense Regular Connective Tissue

Dense Irregular Connective Tissue Similar to areolar connective tissue but collagen fibers are much thicker. Similar to areolar connective tissue but collagen fibers are much thicker. Fibers run in different planes making this a very strong tissue and resistant to strong tensions from all directions. Fibers run in different planes making this a very strong tissue and resistant to strong tensions from all directions. Found in dermis; fibrous capsules surrounding kidneys, bones and lymph nodes; and in the submucosa of the GI tract. Found in dermis; fibrous capsules surrounding kidneys, bones and lymph nodes; and in the submucosa of the GI tract.

Dense Irregular Connective Tissue

Elastic Connective Tissue High content of branching elastic fibers. High content of branching elastic fibers. Very distensible, allows for stretching and returning to original shapes. Very distensible, allows for stretching and returning to original shapes. Found in lung tissue, large elastic arteries, and suspensory ligaments. Found in lung tissue, large elastic arteries, and suspensory ligaments.

Elastic Connective Tissue

Cartilage Three types: Three types: 1. Hyaline cartilage 2. Fibrocartilage 3. Elastic cartilage

Hyaline Cartilage Consists of a dense network of collagen fibers embedded in a gel-like ground substance containing chondroitin sulfate with chondrocytes situated in lacunae. Consists of a dense network of collagen fibers embedded in a gel-like ground substance containing chondroitin sulfate with chondrocytes situated in lacunae. Matrix appears homogeneous and clear of fibers. Matrix appears homogeneous and clear of fibers. The predominant cartilage found in the trachea, bronchi, articular cartilages, nose and ribs. The predominant cartilage found in the trachea, bronchi, articular cartilages, nose and ribs.

Hyaline Cartilage

Elastic Cartilage Consists of chondrocytes located in lacunae surrounded by a network of elastic fibers. Consists of chondrocytes located in lacunae surrounded by a network of elastic fibers. Found in epiglottis, pinna of the ear and the internal auditory canal (Eustachian tube) Found in epiglottis, pinna of the ear and the internal auditory canal (Eustachian tube)

Elastic Cartilage

Fibrocartilage Consists of chondrocytes in lacunae scattered among bundles of collagen fibers. Consists of chondrocytes in lacunae scattered among bundles of collagen fibers. Most predominant in intervertebral discs, pubic symphysis, and menisci of knee joints. Most predominant in intervertebral discs, pubic symphysis, and menisci of knee joints.

Fibro cartilage

Bone Two types: Compact and Spongy Compact bone consists of osteons (Haversian systems) osteocytes in lacunae and lamellae. Compact bone consists of osteons (Haversian systems) osteocytes in lacunae and lamellae. Spongy bone is characterized by trabeculae surrounded by spaces filled with red bone marrow Spongy bone is characterized by trabeculae surrounded by spaces filled with red bone marrow

Bone Two types: a) Compact b) Spongy Two types: a) Compact b) Spongy

Compact Bone

Blood Consists of liquid portion (plasma) Consists of liquid portion (plasma) Erythrocytes (RBC) Erythrocytes (RBC) Leukocytes (WBC’s = 5 types) Leukocytes (WBC’s = 5 types) Platelets (Thrombocytes) Platelets (Thrombocytes) Functions to carry nutrients and waste products to and from tissues as well as protect body against foreign invaders and infection. Also active against bleeding maladies and hemorrhage. Functions to carry nutrients and waste products to and from tissues as well as protect body against foreign invaders and infection. Also active against bleeding maladies and hemorrhage.

Blood

Erythrocytes Small anucleated cells in blood Small anucleated cells in blood Donut shaped Donut shaped Most numerous cells in a blood smear Most numerous cells in a blood smear

Leukocytes Includes Agranulocytes and Granulocytes. Includes Agranulocytes and Granulocytes. Agranulocytes: lymphocytes and monocytes Agranulocytes: lymphocytes and monocytes Granulocytes: neutrophils, eosinophils and basophils Granulocytes: neutrophils, eosinophils and basophils Never Let Monkeys Eat Bananas (Most abundant to least abundant) Never Let Monkeys Eat Bananas (Most abundant to least abundant) neutrophils>lymphocytes>monocytes>eosin- ophils>basophils neutrophils>lymphocytes>monocytes>eosin- ophils>basophils

Leukocytes

Neutrophils Medium-sized leukocytes (10-12 um) Medium-sized leukocytes (10-12 um) Most numerous white blood cells (60-70%) Most numerous white blood cells (60-70%) Granular cytoplasm but granules not easily discernable Granular cytoplasm but granules not easily discernable Nucleus is multi-lobed and variable shaped Nucleus is multi-lobed and variable shaped Lymphocytes Nucleus is spherical and dark purple inside pale blue cytoplasm (5-17 um) Second most prominent wbc (20-25%)

Monocytes Largest of the wbc’s (14-24 um) Largest of the wbc’s (14-24 um) Third most abundant wbc’s (3-8%) Third most abundant wbc’s (3-8%) Nucleus is “U” or kidney shaped Nucleus is “U” or kidney shaped Cytoplasm is bluish in color Cytoplasm is bluish in color Eosinophils Nucleus is bi-lobed Reddish cytoplasmic granules Similar size to neutrophils (10-14 um) Fourth most abundant wbc’s (2-4%)

Basophils Nucleus is bilobed; (8-10 um) Nucleus is bilobed; (8-10 um) Large blue-purple cytoplasmic granules Large blue-purple cytoplasmic granules Least common wbc (0.5-1%) Least common wbc (0.5-1%)

Leukocytes summary

Body membranes Cutaneous membranes = skin (more later) Cutaneous membranes = skin (more later) Mucous membranes = line body cavities that open directly to the exterior (digestive, respiratory, reproductive and urinary tracts). Mucous membranes = line body cavities that open directly to the exterior (digestive, respiratory, reproductive and urinary tracts). Serous membranes = line body cavities not directly open to exterior Serous membranes = line body cavities not directly open to exterior Synovial membranes = line joint cavities Synovial membranes = line joint cavities

Mucous membranes Vary considerably throughout the body where they exist. Vary considerably throughout the body where they exist. Are an important barrier to foreign microbes and agents that could invade the body. Are an important barrier to foreign microbes and agents that could invade the body. Composed of epithelial tissues with underlying connective tissue support. Composed of epithelial tissues with underlying connective tissue support. Contain numerous mucus and goblet cells that keep the membranes moist. Contain numerous mucus and goblet cells that keep the membranes moist.

Serous Membranes (SM) Composed of areolar (loose) connective tissue and covered by simple squamous epithelium Composed of areolar (loose) connective tissue and covered by simple squamous epithelium Serous membranes line body cavities that are not exposed to the outside and also cover the organs within the cavities. There are 2 layers with a space between them. Serous membranes line body cavities that are not exposed to the outside and also cover the organs within the cavities. There are 2 layers with a space between them. Parietal layer = attached to body wall Parietal layer = attached to body wall Visceral layer = covers and attaches to organs Visceral layer = covers and attaches to organs Serous fluid = clear fluid between two layers Serous fluid = clear fluid between two layers

Specialized Serous Membranes Pericardium = serous membrane surrounding the heart as a sac and covering the heart. Pericardium = serous membrane surrounding the heart as a sac and covering the heart. Pleura = serous membranes lining the thoracic cavity and covering the lungs. Pleura = serous membranes lining the thoracic cavity and covering the lungs.

Specialized Serous Membranes Peritoneum = serous membrane lining the abdominal cavity and covering most abdominal organs, except the kidneys, duodenum, and parts of the colon. Peritoneum = serous membrane lining the abdominal cavity and covering most abdominal organs, except the kidneys, duodenum, and parts of the colon.

Synovial membranes Line joint cavities Line joint cavities Consist of fibrous connective tissue and enclose the joint cavities. Consist of fibrous connective tissue and enclose the joint cavities. This will be covered in greater detail in the next unit when we talked about joints and articulations. This will be covered in greater detail in the next unit when we talked about joints and articulations.

Muscle Three types 1. Skeletal muscle 2. Smooth muscle 3. Cardiac muscle

Skeletal Muscle Most prominent characteristic is parallel large cylindrical cells with multiple nuclei. Most prominent characteristic is parallel large cylindrical cells with multiple nuclei. Cross-striations are present. Cross-striations are present. Voluntary muscle; under willful control. Voluntary muscle; under willful control. Attached to bones and tendons and skin. Attached to bones and tendons and skin.

Skeletal Muscle

Cardiac muscle Branching cells that interdigitate as a syncytium. Branching cells that interdigitate as a syncytium. Intercalated discs present at cell junctions. Intercalated discs present at cell junctions. Generally uni-nucleate Generally uni-nucleate Found in walls of heart only (myocardium) Found in walls of heart only (myocardium) Characterized by auto-rhythmicity Characterized by auto-rhythmicity Involuntary muscle Involuntary muscle Cross striations are present. Cross striations are present.

Cardiac muscle

Smooth Muscle Cells are spindle shaped Cells are spindle shaped Single nucleus Single nucleus DOES NOT HAVE cross striations DOES NOT HAVE cross striations Involuntary muscle Involuntary muscle Found in walls of most hollow organs (vessel walls, intestinal tract walls, reproductive tract, urinary tract, respiratory tract, etc.). Found in walls of most hollow organs (vessel walls, intestinal tract walls, reproductive tract, urinary tract, respiratory tract, etc.).

Smooth Muscle

Nervous tissue Two cell type: Neurons and neuroglial cells Two cell type: Neurons and neuroglial cells Neurons are branching elongated cells, highly specialized for generating nerve impulses. Neurons are branching elongated cells, highly specialized for generating nerve impulses. Neuroglial cells are of multiple shapes and functions and are considered as supporting cells. Neuroglial cells are of multiple shapes and functions and are considered as supporting cells.

Nervous tissue Neurons and neuroglial cells Neurons and neuroglial cells