Tissues

Tissue is…. A collection of cells organized for a particular function Collections of tissue are then arranged into organs

Tissue types Mammals have 4 basic tissue types Epithelial Connective Muscle Nerve

Epithelial Tissue Collections of cells packed together is sheets They lie the body’s surface and openings They also cover the openings of the Intestinal tract Reproductive tract Urinary tract They line the tubes in the body such as blood vessels and heart

Epithelial functions Functions of epithelial 1. Defense 2. Secretions Skin, respiratory tract   2. Secretions Tears and saliva help to moisten the tissue Urine and sweat Milk from mammary

Functions of Epithelial 3. Absorption Very highly selective Intestines, lungs and kidneys absorb from surrounding fluid Cells lining the blood vessels provide point of exchange for materials in the blood and ECF   4. Conserve materials Prevent excess loss of fluid and nutrients from the ECF

Epithelial Every epithelial tissue (ept tissue) has an underlying connective tissue layer  > Ept tissue has no direct blood flow so the connective tissues provide 1. Support 2. Nutrients 3. Removes waste

Classifications of Epithelial 1. Simple One cell layer  2. Stratified Multiple layers  3. Transitional Multiple layers with the shape of the cell changing

Shape of cells 1. Squamous 2. Cuboidal 3. Columnar Very flat Cube shaped  3. Columnar Taller than they are wide The 2 most appropriate terms are combined to describe the tissue

Cell shapes Simple squamous epithelium Single layer of flat cells Located where there is need for exchange Ex: blood vessels are lined with it for transfer of fluids, nutrients and gases and wastes

Cell shape Simple cuboidal Ept Single layer of cells that are almost square Located in many glands and tubules of the kidneys Functions – secretions or absorption

Cell Shapes Simple columnar ept A single layer of cells that are taller than wide Located in glands, stomach and intestines Stratified cuboidial and columnar also exist in certain glands and ducts Stratified squamous ept Ex: skin

Cell shapes Transitional Ept Specific to urinary tract only It can be stretched Relaxed it looks several layers thick As bladder fills, stretches, when full it seems on a few cells thick It also can prevent exchange of fluid between urine and underlying tissue

2 way barrier over the body Functions Integument Also called skin 2 way barrier over the body Functions Damaging agents are kept out Fluid and nutrients are kept in

Specialized skin cells Hair, fur and sweat glands Help maintain stable body temp   Pigment Protects body from UV radiation Clinically the skin is the first impression of an animals overall health. Many diseases appear on the skin – fleas, hair loss and skin sores Parasitic, nutritional and endocrine diseases affect the skin

Skin Skin – 2 layers 1. Epidermis 2. Underlying dermis Epidermis   Epidermis Stratifies squamous ept Originated from the basal layer and move outward and shed from the surface Dermis Connective tissue layer that contains Blood vessels Nerves Glands

skin Hypodermis 2nd layer of connective tissue Supports the skin (epidermis with dermis) Hypo = beneath

Specialized skin cells The footpads/digital pads of dogs and cats are specialized skin cells Thickened layer Resist physical trauma A pad of fat is under this to act as a cushion

Hair Is a Modification of epidermal cells Functions 1. Insulation   Functions 1. Insulation 2. Protection 3. Sensation

Hair Originates from the follicle in the dermis Hair shaft is made of Ept cells Growth occurs as cells are attached to the base of the hair

Arrector Pili Muscle that is attached to the connective tissue around the hair follicle Contracted = the hair stands upright Cold weather improves insulation effect of the hair.

Claws and hooves - Modified epidermis

Keratin A specialized protein that is deposited in the cells Gives hardness and durability The claws of dogs and cats surround the last bone of the toe Hooves are similar to claws The last bone of the equine foot is suspended within the hoof

Laminar Corium Supports and nourishes the hoof wall Is connective tissue   Growth of the hoof Occurs in the coronary band when cells are deposited

Horns The same as hoof and claw The center of the horn is a bone that surrounding tissues supplies blood to feed Horn material is called keratinized epithelium

Muscle tissue 3 muscle types exist in mammals - Skeletal - Smooth   3 muscle types exist in mammals - Skeletal - Smooth - Cardiac

Skeletal Attaches to the skeleton Allows for motion Under voluntary control Animals move with nerve signals

Smooth Muscle Involuntary muscle Located in many hollow organs of the body Ex: blood vessels Gastrointestinal tract - Urinary bladder

Cardiac muscle Located in the heart Involuntary Skeletal muscle is striated voluntary muscle  A muscle consists of thousands of muscle fibers or muscle cells

Myofiber An entire muscle cell Have several nuclei Lots of mitochondria Organized in parallel rows Separated by connective tissue that includes blood vessels and nerves

The ability of a muscle fiber to contract is a very complicated system Within the fiber – an organized system of myofilaments exist

2 proteins make up the filaments Actin Myosin They are all organized along the length of the cell

During contraction the actin and myosin filaments slide along each other The filaments have small bridges between them that bind and release as they slide   The contraction starts originally with the stimulation from a nerve cell

The stimulation releases calcium stored in the endoplasmic reticulum This flow of calcium ions causes the filaments to slide across each other A large amount of mitochondria are present to provide energy.  During relaxation, the cell will actively transport calcium back to the endoplasmic reticulum

Porcine Stress Syndrome (PSS) Genetically transmitted disease in which the calcium is not transported back to the endoplasmic reticulum This causes muscles not to relax Occurs when pigs are stressed for heat or transportation

Rigor Mortis Muscle stiffness Occurs at death because there is no energy to pump the calcium back to the endoplasmic reticulum With energy, muscles can not relax

Hypocalcemia Dairy cattle develop a lack of calcium around calving time The cow drastically increases calcium for mild production So much calcium is excreted in the mild that the levels on the blood and muscles becomes too low The cow becomes weak and unable to stand

Hypocalcemia Treatment Calcium solution placed directly into the bloodstream Within minutes the cow can stand Muscles will grow or shrink based on usage and nerve damage

Sweeny Damage to the shoulder nerve in a draft horse causing the muscle to shrink

Cardiac Muscle Striated and involuntary Myofilaments look the same as skeletal and contraction procedure is the same No nerve stimulation is necessary for contractions Specialized pacemaker cells are responsible for the rate of contraction

Cardiac Nerve cells are present to help influence the rate of contraction The automatic nervous system can increase or decrease the rate As long as there is oxygen and glucose provided to the muscle cells – the heart beats

Smooth Lacks striation Contains actin and myosin filaments but not in the same arrangement Each myofiber is spindle shaped and tapered at each end Each cell has only one nucleus

Smooth Muscle Arranged in sheets around hollow openings Contraction makes opening smaller Example: contraction in blood vessels Contract much slower than skeletal muscle Maintain the contraction longer Controlled by the automatic nervous system

Nerve Tissue Allows communication among areas of the body Located in brain and spinal cord Brain and spinal cord together is called the central nervous system

Peripheral Nervous System Nerves located outside of brain and spinal cord

Neurons Cells in nerve tissue Large Body of it holds the nucleus and other organelles

Axon A hair like extension from the cell body Carries nerve impulses Can end on either tissues or other neurons Axons from many neurons bundle together to form a nerve Can be very long Example: horse – can be 2 meters long  

Dendrites Other extensions of the neuron Axon often ends on a dendrite of another neuron The site of this connection is called a synapse When stimulated, the dendrite begins the nerve impulse

How nerve impulses happen Flow of ions passes through cell membrane In a resting nerve cell – sodium ions are actively transported into extra cellular fluid At the same time, potassium is pumped into the cytoplasm Stimulation causes ions to flow across the cell membrane Stimulation moves down the axon quickly

Nerve impulses can be measured as an electrical event in the body

3 types of neurons 1. Sensory neurons Have receptors that stimulate in response to an animals change in environment Receptor types Light, heat, touch hearing, balance, taste or smell

2. Interneuron Found within the central nervous system Stimulated by a sensory neuron Allows a pathway that lets the central nervous system control the animals activities  

3. Motor Neurons Begin at central nervous system and extend to a muscle or glands When stimulated – an action occurs Example: muscle contracts = gland secrets   Stimulation occurs by a sensory neuron or an interneuron.