99 terms

Assessment 6- Animal Anatomy

Animal Anatomy
STUDY
PLAY
Parous
female that has given birth
Nulliparous
female who has not given birth
Uniparous
given birth only one time
Multiparous
given birth more than one time
-multiple births
Monotocous
single offspring/gestation
-cows and horses
Polytocous
animals that have litters
-cats, dogs, pigs
Ovaries
Paired glands found in the lumbar region of the abdominal cavity
-constantly changing as follicles develop towards the surface (do NOT change during pregnancy tho)
-follicle ruptures at ovulation, releasing the ovum
--Corpus hemoragicum and then corpus luteum form at ovulation site
Ovaries: two functions
endocrine: hormone producing
Cytogenic: cell producing
Ovaries: cytogenic functions
the ovary is encapsulated in a dense connective tissue capsule, called the tunica albuginea.
the cortex (outer portion) of the ovary consists of dense, irregular connective tissue interspersed w.
-Follicles (containing developing ova) in various stages of development
--Corpus hemorrhagicum- blood filled
--Corpus luteum- yellow body
--corpus albicans- white body
Tunica Albuginea
the ovary is encapsulated in a dense connective tissue capsule, called the tunica albuginea
Mature follicle
when matures, the follicle ruptures and becomes corpus hemorragicum (red) then corpus luteum (yellow)
Before puberty
millions of primordial follicles
once you hit puberty
primordial follicles becomes primary follicles
-only have a few graafin follicles that will develop
-Species with litters have numerous graafin follicles
Graafin follicles
the number you have is the number you will ovulate when its that time
-they degenerate when not used
-large dominant follicle
Oocyte
surrounded by a layer of cboidal epithelium or follicular cells (granulosa cells)
Ovulation
involves thinning of tissue layer and changes in follicular fluid pressure
Menopuase
have no more eggs
-It is an effect of modern day life (you used to only live to be about 40 yrs/old so you never reached the time when you did not have any eggs left)
Testes 2 Functions:
Cytogentic: produce sperm
Endocrine: produce testosterone
Descent of the Testes
When born, the testes are in the abdominal cavity
-they drop with age because they need to be at a lower temp than the body to produce viable sperm
-The testes descend thru the inguinal canal
-The goobernaculum pulls the testes thru layers of muscle and pulls peritoneum with it
Inguinal hernia
if the inguinal ring and canal are too large, a loop of intestine may pass thru the canal into the scrotum, producing an inguinal hernia
Cryptorchidism
When an animal's testes fail to descend into the scrotum
- A cryptorchid with both testes retained in the abdominal cavity is likely to be sterile
-An unilateral cryptorchid is fertile as long as the one descending testical produces normal sperm
-Does not interfere with testosterone production
-It is a genetic trait
Testes: three layers
There are three layers of connective tissue
-parietal vaginal tunic
-visceral vaginal tunic
-tunica abuginea(tough fibrous capsule that lies directly on the surface of the testes)
Scrotum
cutaneous sac that conforms in size and shape to the testes it contains
- during exposure to cold, the muscle fibers of T. dartos and the M. cremaster contract, and help hold the testes against the body wall
scrotum: tunica dartos
a layer of fibroelastic tissue mixed with smooth muscle fibers the lies immediately under the skin
Scrotum: scrotal septum
divides the scrotum into two compartments
Scrotum: Cremaster muscle
a slip of internal abdominal oblique muscle
-contracts when cold to pull scrotum closer to body and warmer
Testes: Seminiferous tubules
most of the mass of the testes is from this
-site of the formation of sperm
-mass of coiled tubules surrounded by the tunica albuginea
-system of ducts that transports sperm cells way from the seminferous tubules
--rete testes
--efferent ductules
Pathway of sperm
path that sperm travel from formation until they exit the body
-seminiferous tubules
-exit to the rete ductules
-efferent ductules
-head, body, and tail of epididymus
-Ductus deferens (vas deferens) ascends from the tail of the epididymus, thru spermatic cord and inguinal ring, into abdomenal cavity
-urethra
-penis
rete testis
network of tubules into which sperm are delivered from the seminiferous tubules
interstial (Leydig) cells
found in the connective tissue between the seminferous tubules
-secrete testosterone
Sustentacular cells (Sertoli cells)
found within the seminferous tubules
-nourish the developing sperm
Epididymis
composed of a long convoluted tube that connects the efferent ductules of the testis with the ductus deferens (vas deferens)
-Houses the sperm as they reach maturity and become motile before they are expelled by ejaculation

Consists of three parts:
-Head: in which the efferent ductules empty
-Body: lies on the long axis of testes
-Tail: continues as the ductus deferens, which conveys sperm from the testes to the urethra
Ductus deferens (vas deferens)
continuation of the tail of the epididymis
-muscular tube composed mainly of smooth muscle
-Undergoes peristatic contraction during ejaculation, propelling sperm from the epididymis to the urethra
Spermatic Cord
suspends each individual testes within the scrotum
-blood vessels, nerves, lymphatics, ductus deferens, cremaster muscle are all located here
Accessory Reproductive Glands
the male accessory sex glands produce the bulk of the ejaculate or semen, the medium for the transport of sperm (exocrine)
-the products of these glands serve to nourish and activate the sperm, to clear the urethral tract prior to ejactulation, serve as the vehicle of transport of the sperm in the female tract, and to plug the female tract after placement of the sperm to help ensure fertilization
The Accessory Reproductive Glands
-Ampullary glands
-Vesicular glands
-Prostate glands (produces an alkaline secretion. In older, intact males, it becomes enlarged and may interfere with urination)
-Bulbourethral glands
Penis
the internal strucutre of the penis consists mainly of cavernous, erectile tissue, which is a collection of blood sinuses separated by sheets of connective tissue. Some mammals have a lot of cerectile tissue relative to connective tissue
- The urethra is on the ventral side of the penis

There are two types:
1.) Fibroelastic penis: boars and ruminants
2.) Musculocavernous penis: horses, dogs, cats

-Male organ of copulation, 3 gen. areas:
Glans, body, base (root), prepuce
Fibroelastic Penis
Body of penis primary composed of fibroelastic tissue
-Requires little blood to achieve full erection
-Stiffening without a change in diameter
-Sigmoid flexure: (S- shaped) when this straightens out it causes the elongation of the fibroelastic penis
-Retractor penil muscle: relax during erection and tight after ejaculation
Musculocavernous Penis
Stallion, dogs, primates, and cats
-Body of the penis contains more muscle and less fibroelastic tissue
-Blood fills the sinuses within the penis (corpus cavernosum) during erection and increases the diameter and length with stiffening
-Dogs and Cats: distal end of the cavernosum ossifies to become the os penis (bone)
Prepuce
Fold of skin that covers and protects the head of the unerect penis
-Decreases external irritation or contamination of the glans and urethral orifice
-Is stretched out during erection
Homeostasis
is the process of maintaining normal body processes

-Two systems in the body provide communication and control homeostasis
1.) Nervous System: electric nerve impulses, provides sensory information
2.) Endocrine System: hormones transported thru the bloodstream
Endocrine System
1.) Glands: ductless, secrete into the blood stream
2.) Hormones (messengers): chemical substances (proteins, amino acids, steroids) that are produced by special ductless glands in one part of the body and travel thru the blood to a target cell in order to produce a specific regulatory effect
3.) Target Organs: tissue with a final biological response to the hormones
Hypothalamus
Located in the floor of the third ventricle of the brain
-Receives sensory input via the nervous system
-It is the link between the two communication systems in the body (Translator)

-It secretes releasing factors that cause the pituitary to release appropriate hormones (TRH, GnRH)
Anterior Pituitary
Hormones:
1.) Adrenocorticotropin (ACTH)- released as a pre-cursor in stress
2.) Thyroid Stimulating Hormone (TSH)- stimulates thyroid to release thyroid hormone
3.) Follicle Stimulation Hormone (FSH)- to the ovary and testes
4.) Luteinizing Hormone (LH)- stimulates testosterone production in men, and regulates the menstral cycle and ovulation in women
5.) Growth Hormone (GH)-stimulates growth, cell reproduction/regeneration in humans and other animals
6.) Prolactin (PRL)- stimulates breast development and milk production in women
Posterior Pituitary
Anti-diuretic Hormone (ADH): helps manage the amount of water in the body by acting on the kidneys.
Oxytocin: stimulates milk let down and contractions of the uterus
Thyroid Gland
Located on either side of trachea just outside thoracic cavity

Follicular Cells:
-Secrete throxine (T4) & triiodothyronine (T3)
-T3 is the biologically active form
-Thyroid hormone regulates basal metabolic rate, oxygen use, cellular metabolis, normal growth

Parafollicular Cells: (around the follicular cells)
-Secrete calcitonin
-Released in response to high blood calcium concentration (If too high it can calcify your organs!)
-Reduces [Ca] by inhibiting osteoclasts, reduces GI absorption Ca, increases urinary loss of Ca
Pineal Gland
Located in the brain (TINY size)
-Shaped like a pine cone
-Produces melatonin (moderates sleep/wake cycles, seasonal functions like seasonal breeders or animals that hibernate)
-Light signal necessary to set circadian rhythms are sent from the eye thru the retinohypothalamic system to the pineal gland

-Crucial in animals that hibernate
Parathyroid Glands
embedded in the thyroid glands like little buttons

-Parathyroid hormone (PTH)
-Increased in response to low blood [Ca]
-Stimulates osteoclasts, increases GI absorption of Ca, decreases urinary loss of Ca
Adrenal Gland
hormones secreted by the adrenal glands help the body cope with stress
--stress can be because of shock/blood loss/ finals etc.
-Cortex: area under the capsule

The outer cortex is divided into three zones:
1.) Zona glomerulosa
-mineralocorticoids (aldosterone)
-increases blood pressure by increasing fluid retention by kidneys

2.) Zona fasciculata:
-Glucocorticoid (cortisol)
---long term exposure to cortisol can give you metabolic disease
-Catabolic, increases glucose (energy) production, antiinflammatory, inhibit immune function, protein breakdown in muscles
-why stressed people often get sick^^

3.) Zona reticularis
-produces small amount of weak androgens (DHEA), which is like a weak form of testosterone and builds muscle

-The inner medulla is an extension of the sympathetic nervous system
--Epinephrine & norepinephrine increase during stressful or emergency situations. They increase cardiac output, BP, blood glucose levels for 'flight or flight'
Endocrine Pancreas
1.) Alpha Cells produce glucagon
-glucagon stimulates glucose production in the liver
-glucagon is catabolic (breaks down something else)
-Low blood sugar stimulates glucagon secretion

2.) Beta cells produce insulin
-Insulin increases glucose transport into cells
-Insulin in anabolic
-High blood sugar stimualtes insulin secretion, which decreases blood glucose levels

3.) Delta cells produce somatostatin, gastrin:
-pancreatic somatostatin modulates release of both insulin and glucagon to prevent oversecretion of either hormone
-Gastrin increases HCl production in stomach
Ovary Endocrine
-Progesterone (from CL) and estrogen (from follicles) are the main steroid hormones produced
-FSH from anterior pituitary induces follicle growth. Follicles produce estrogen
-LH from anterior pituitary stimulates synthesis of the corpus luteum after ovulation. CL produces progesterone
-Ovary can also produce relaxin, which aids in dilation of the cervix and relaxes ligaments of the birth canal
Testes Endocrine
-Testicular function is regulated by anterior pituitary LH and FSH
-Testosterone is the main androgen produces
-LH stimulates Leydig cells; testosterone synthesis
-FSH and androgens stimulate sperm production
Closest related species to birds
reptiles and dinosaurs
-we know because of bone structure
Avian Skeleton
Skeleton is light, compact, and strong
-They have thin, brittle cortices because they are higher in calcium phosphate than mammals bone
-their key adaptation is their fusion of the bones to strengthen and stiffen their skeleton and to keep their posture
-There are air sacs in the bone (Pneumatic)- and if they break a bone it could affect their respiratory system
-There is an abundance of spongy medullary bone found in long bones of sexually mature females--provides a source of calcium for eggshell production (esp. important for chix laying eggs)
Avian Skeleton: Skull
- Large orbits
-Single occipital condyle (can turn their heads about 180 degrees around)
-They have a scleral bone (looks like a ring inside the orbit) within their orbit and they cannot move their eyes within the orbit, instead they have to turn their heads so their eyes can move
-Beak- attaches to the upper and lower jaws. There are many variations among diff. species of birds
--Birds sometimes need a beak trim so their upper and lower beak tips align properly- they need them to align so they can properly eat
Avian Beak Variations
-Ducks: have tough, connective tissue "teeth" that allow them to filter water for plants, insects, etc
-Pelicans: pouch that scoops up fish, water
Avian Axial Skeleton: Vertebrae
-Single occipital condyle: able to rotate head to greater degree (180 ^o) than mammals
-Avian neck is long and freely moveable (they have 8-25 cervical vertebrae)
-Wings are highly specialized, the highly mobile neck is needed for preening (to straighten and clean its feathers with its beak)
-Last 1-2 thoracic vertebra are fused with lumbar, sacral, and first couple of coccygeal vertebrae to form the SYNSACRUM
--This fusion helps to create a stiff body
-There are lateral extensions on the ribs that overla, bracing together to form a sturdy cage that will protect heart and lungs during flight
-Fusion creates a rigid dorsal axial skeleton--necessary for maintaining body posture during flight
Avian Axial Skeleton: Chest/Sternal Area
-A birds chest doesnt expand when breathing in and out becuase they do NOT have a diaphragm
-They have a coracoid bone between their shoulder and sternum that helps stabilize the shoulder
-They have fused clavicles (Wishbone)- attached to coracoids and sternum by tough connective tissue
-Their sternum is a large unsegmented bone
--Keel: (or breastbone) large and bladelike, thin slab of bone which the massive flight muscles are attached to
Avian Axial Skeleton: Pelvis
Pelvic bones are fused to the synsacrum
-Pubic bones are not fused ventrally because they need to be expandable when laying eggs
Avian Appendicular Skeleton: Front limb (Wings)
To provide sturdy support for the flight feathers, the bones of the "hand" are reduced and fused
-Humerus
-Radius, ulna
-2 carpal bones (b/c of fusion)
-carpometacarpal bones (fusion)
-Digits
Avian Appendicular Skeleton: Hind limbs (legs)
Landing puts a toll on the body so their legs must be strong!
-Femur
-Tibiotarsus, fibula (tibia has fused with some of the tarsals)
-Tarsometatarsus
-Digits
--generally 3 oriented facing forward, one pointing caudally (for perching)
Different Variety of toes
Duck: Broad, webbed feet for swimming
Hawk: sharp, hooked claws for gripping
Flamingo: long, wide-spaced toes for wading
Partridge/Pigeon: short toes for walking
Finch: Long, strong toes for perching
Muscles: White muscle
"White meat"
-Pectoral muscle of chickens and turkeys (Dont fly much) are white muscle
-More powerful, but less endurance
Muscles: Red Muscles
"Dark Meat"
-Contain large amounts of myoglobin (carries oxygen)
-Sustained effort- like flying
-Pectoral muscles of good fliers are red muscle, not white muscles
---reason why duck breast meat is more oily, because it is more red meat than white meat becuase they are good fliers
Avian Integument
Avian Skin: thin and loose, tears easily, poorly supplied by nerves and blood vessels
-soft ornamental outgrowth of skin (comb, wattles, ear lobe)- helps the bird get rid of excess heat (heat is worse for a bird than cold)
-lots of fat underneath the skin

Beak: derivative of skin, richly innervated
-will hit corium (quick) and bleed is cut too short

Sebaceous Gland- preen gland
-only skin gland present other than in external ear and vent
-Secretion carried to feathers during preening
-Secretion is an oily substance that helps waterproof the bird
Skin: Wattle
located underneath the 'chin' and beak of the bird
Skin: Comb
located on top of the head
-should be standing upright
-if the comb is blue/pale, or limp it can mean that the bird has a respiratory problem
-When dehydrated- the comb will fall over and legs can also show signs too (they can be withered and tinted)
Avian Feathers
-Highly specialized epidermal structures
-Derived from scales of reptiles

Feathers Functions:
- flight
-provide insulation
-Deflect rain/snow
-Serve as camouflage (snow owl)
-courting or agressive displays

-Feather muscles (similar to mammals erector pili muscles- which are erect when you get goosebumps) elevate or lower groups of feathers
--like a peacock lifting its tail feathers into a fan
Feather Types: Flight/Contour Feathers
Contour/Flight feathers: externally visible.
-Main shaft
-Closed Vane (closed sheath of feathers)
--barbs
--minute barbules
--microscopic hooks on distal barbules, loosely engage those that cross under them and form closed vane- kind of like velcro

(PIC)
Feather Types: Down Feathers
-feathers for insulation
-No barbs or hooks at all
-No closed vane (not a closed sheath of feathers)
-Haphazard arrangement gives fluffy appearance and creates dead air space for warmth

(PIC)
Avian Cardiovascular System
-Four-chambered heart, like mammals
-Has a very large heart relative to their body size
- Avian hearts are stronger and beat faster than mammalian hearts
--higher cardiac output and higher heart rate
Avian Respiratory System
-Flight requires a high metabolic rate, which in turn requires a lot of Oxygen
-Avian lungs are relatively small and non-expansive
-No pleural cavity-no diaphragm
-Intricate set of air sacs allow unidirectional ventilation of lungs
-No mixing of oxygen rich and oxygen-depleted air
-Air sacs are not for gas exchange, but to store air and act as a bellows
Pattern of Air Movement Thru Avian Respiratory System
*Always 2 things happening at once**

1.) Inhalation: fresh air moves into the caudal air sacs
2.) Exhalation: that bolus moves into the lungs (air exchange)
3.) Inhalation: Oxygen depleted air moves into cranial air sacs
4.) Exhalation: bolus of air is expired
Avian Digestive System: Mouth
Birds have no lips, soft palate, cheeks, or teeth
-cannot chew their food (use gizzard and proventrilicus)
-Beaks/bills are made of epidermal tissue
-The hard palate (palatine, maxillary and pre-maxillary bones) divided by a long, narrow slit in the center that is open to the nasal passage
-This opening and the absence of a soft palate make it impossible for the chicken to create a vacuum to draw water into its mouth; it has to scoop water, elevate its head, and let the water run down its esophagus by gravity
Avian Digestive System: Esophagus
Food passes thru the esophagus (Gullet) on its route from the back of the mouth (pharynx) to the proventriculus
-The crop: a pouch just before the esophagus enters the body cavity
-Acts as a storage space for food
-Little or no digestion takes place in this organ
Avian Digestive System: Stomach
-Most marked area of species variation

Fish and flesh-eating species: have only a proventriculus (glandular stomach) only
-HCl and pepsin are produced here

Herbivorous diet: mechanical reduction of tough material in the gizzard just after leaving the proventriculus
Avian Digestive System: Gizzard
- The gizzard is also known as the muscular stomach
-Lies between the proventriculus and the duodenum (upper small intestine)
-Contains very powerful muscles and a thick mucosa
-Contractions take place when food enters gizzard
-Abrasive material such as grit, rocks, gravel, etc. help grind food into smaller particles
Avian Digestive System: Small Intestine
About 62 inches long in the av. adult chicken
-First part is the duodenal loop which holds the pancreas
--The pancreas secretes the enzyme amylase, lipase, and trypsin
-After the duodenal loop, the jejunum and ileum follow
Avian Digestive System: The Ceca
Two blind pouches between the small and large intestine
-There is a sphincter at the proximal end of each
-Contains a lot of lymphoid tissue
-Bacterial breakdown of cellulose

Pigeons/Passersine: have a short ceca
Carniverous Birds: do NOT have a ceca
Avian Digestive System: Cloaca
Common to the digestive & urogenital systems
-Cloaca means "common sewer"
-Opens to the exterior (vent)
-Colorectum, ureters, ductus deferens (or left oviduct) enter at various levels
Avian Digestive System: Vent (Anus)
External opening of the cloaca
-Size varies greatly in females depending on egg production status
Avian Male Reproductive System
Consists of paired testes, epididymides, & vas deferens all in abdomen
-Testes do not descend (no spermatic cord, vaginal tunic, scrotum)- heat is not a problem
-No urethra, no accessory repro. glands
-Testes are large and white during breeding season
-Epididymis is not divided into head, body, and tail like mammals
-Ducts of the testes lead to the vas deferens which carry sperm from the testes to the papillae in the cloaca
-Sperm are stored in the vas deferens. Diluted with lymph fluid and ejaculated as a mixture during copulation
-Phallus of chick is small, but waterfowl have a well-developed organ capable of intromission
Avian Female Repro. System
-Consists of an ovary and an oviduct
-Two ovaries and oviducts during embryonic development, but right side atrophies at hatching leaving only the left ovary and oviduct
-Mature ovary looks like a bunch of yellow grapes
-Follicle consists of a large, yolk-filled oocyte
-No corpus luteum develops
-Oviduct is site of fertilization (like in mammals)
-Sperm are also stored in the oviduct for up to 10 days
-Oviduct conducts fertilized ova to the cloaca

Along the way:
-Infundibulum: 15 minutes (forms the chalaziferous layer)
-Magnum: 3 hrs. (adds much of the albumen)
-Isthmus: 1 hr. (Encloses the embryo in membranes)
-Uterus: 20 hours (Produces the shell; "shell gland")
Uterine Tubes (Oviducts)
Paired convoluted tubes that conduct the ova from each ovary to the respective horn of the uterus
-Site of fertilization
-The portion of the uterine-tube adjacent to the ovary is expanded to form a funnel-shaped infundibulum that takes an active part in ovulation by directing the ovum into the uterine tube
-Fimbria are finger-like projections lining the infundibulum
--They help to "catch" the ova and conduct it into the oviduct

Fluids produced by the oviduct:
-support ovum and nourish it too
-Support sperm
-Important for fertilization (fluid brings egg and sperm together)
-Help nourish the early embryo

(PIC)
Ectopic Pregnancy
when the egg is ovulated its completely free in the abdominal cavity
-Ectopic pregnancy happens when pregnancy happens in the wrong place (like the abdominal cavity)
Uterus
consists of a muscular body, cervix (neck), and two horns (horns are long in polytocous species that have litters- like dogs and pigs)
-relatively proportions of each compartment vary considerably with species
--Relative to the extent of the horns, the body of the uterus is largest in the mare, less extensive in the ruminant and small in the sow(because they have large uterine horns)

-The mucosa lining the uterus, the endometrium, is highly glandular tissue that varies with thickness and vascularity with hormonal changes in the ovary and with pregnancy (Thickest during ovulation, is reabsorbed in animals that do not get their period and is shed in animals that do get a period)

--caruncles are present even on the lining of the non-pregnant ruminant uterus--
-Uterine glands are tubular glands, active during estrus and pregnancy, during which they produce a fluid known as uterine milk
-Secretions are important to survival of preimplantation embryo

-The myometrium is the muscular portion of the uterine wall
-During pregnancy the amount of muscle in the uterine wall increases dramatically, both in cell size (hypertrophy) and in cell number (hyperplasia)
-Helps push the baby out when in labor

-Lining of the uterus changes under the influence of estrogen and progesterone. It becomes thick leading up to and round time of ovulation in order to prepare to receive and nourish a fertilized ovum. If pregnancy does not occur, lining is lost-menstruation in primates. Most do not show any or much blood because lining is simply reabsorbed by body
Types of Uteri
-Mare: bipartile- embryo implanted in one horn or the other
-Cow: bipartile- when there are male/female twins, female will be sterile b/c of exposure to testosterone
-Sow: bicornuate- two, long horns
-Bitch, Queen: bicornuate- two, long horns
-Rabbit: duplex: no uterine body
-Primate: simplex: large body, and small horns

(PIC)
Cervix
Projects caudally into the vagina
-Heavy smooth muscle sphincter that is tightly closed, except during estrus and parturition

Provides:
-lubrication (estrus and pregnancy-to help baby come out)

Barrier during pregnancy to prevent infection, harm to fetus
Vagina
The portion of the repro tract that lies within the pelvis between the uterus cranially and the vulva caudally
-Serves as the birth canal for delivery
Vestibule
The Vestibule is the portion of the repro tract between the vagina and the external genitalia
-The transition between the vagina and vestibule is demarcated by the external urethral orifice
-The vestibule is functionally common to both urinary and repro tracts
Vulva
The vulva is the external genitalia of the female
-It compromises right and left labia, which meet at the midline dorsally and ventrally at the dorsal and ventral commissures

-The ventral commisure is somewhat pendulous and conceals the clitoris, a structure of erectile tissue that has the same embryonic origin as the penis in the male
Mammary Gland
Active at the end of pregnancy and thru out lactation

-Alveoli secrete milk
-Milk collects in the milk cistern (when not milked for awhile the milk cistern is very tight)
-Milk exits from the teat cistern thru the teat canal
-The teat canal is where mastisis can enter (it is warm, has sugar and is a good place for bacteria to thrive)
Placental Anatomy: Placenta
a Fetomaternal organ
-Chorion: fetal portion
-Endometrium: maternal portion
Held together by villi

-Oxygen and nutrients in maternal blood diffuse thru the walls of the placental villi and enter the fetal capillaries
-BLOOD NEVER MIXES
Fetal Membranes
recieves nutrients from the yolk stalk
-amniotic sac: covers the baby when born (white colored)
When the water breaks, its actually
amniotic fluid
When birthing
When the baby is being birthed it will be covered in an amniotic sac (horses)
-The placenta is passed last
-The mother's body releases oxytocin to contract muscles and encourage the placenta to be released
-You do not want the mother to step on the placenta because it could pull and tear them on their inside

-Horses are sensitive to TSS is placenta is left inside for too long
Placental Types
-Diffuse Placenta: (Mare, and Sow)- the connection between the mother and baby overs over the entire placenta

-Zonary Plancenta: (Dog, and Cat)- there is a belt around the placenta where cotyledon and caruncle meet where exchange of gas and nutrients occurs

-Cotyledonary Placenta: (Cow, Goat, and Sheep)
Structures (donut-looking) where exchange occurs
-only in ruminants
-cotyledon: fetal side (hole in donut)
-Caruncle: maternal side (Donut)
-Cotyledon + Caruncle= placentome

Discoid Placenta: (man, and monkey)- disk at the bottom for exchange between mother and baby
Precocial Species
Horses, cattle, sheep, goats, and guinea pigs
-Offspring are born more fully developed
-Offspring are born haired, eyes open, walk and stand more quickly
-Born 'ready to go', tend to be animals of prey
-Tend to have head types that are small and narrow (which are easier for pregnancy)
-Guinea pig is the only rodent that is a precocial species
Altricial Species
Dogs, Cats, Rabbits, and mice
-Offspring are born less developed
-Often blind, unhaired, unable to walk when born
-Mice are born completely blind and there is skin completely covering the eyes. (Their skin is actually completely transparent and you can see in the stomach!)
YOU MIGHT ALSO LIKE...