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level: Ruminants

Questions and Answers List

level questions: Ruminants

Question	Answer
What is the gestation period of the cow?	270-296 days (40 weeks or 9 months)
What is the gestation period of the ewe?	148-152 days (21 weeks or 5 months)
What is the gestation period of the nanny goat?	154 days (22 weeks or 5½ months)
A secondary ovocyte is ovulated and fertilization takes place in the ____ ____.	uterine tube
When fully developed, the chorionic sac occupies the ____ ____ and both ____ ____. The pregnant horn enlarges tremendously; the non-pregnant horn also enlarges, but to a much lesser extent. The fetus usually develops in the horn associated with the ovary that ovulated.	uterine body uterine horns
In the cow, two out of every three pregnancies occur in the ____ horn, probably due to the fact that the rumen effectively occupies the entire ____ half of the peritoneal cavity.	right left
From day ___, the blastocyst begins to elongate bilaterally. It extends the length of the pregnant horn by day ___ in bovine, and by day ___ in the sheep. Later, after extending into the nonpregnant horn, it reaches a length of ___ cm and a width of ___ mm (bovine); in the bovine, the tips of the extended blastocyst are slightly bulbous. The elongated portions of the blastocyst later become folded in a concertina-like fashion; the embryonal disc is visible as a slight swelling in the middle.	12-14 19 14 50-60; 2-5
In the bovine, attachment to the endometrium starts on about day ___ and is complete by day ___; in the sheep and goat, attachment starts on day ___and is complete by day ___.	28; 45 14; 35
The narrow, elongated yolk sac initially extends the length of the ____ ____. The cranial and caudal extensions soon regress and only the central portion remains. The central portion also regresses when the ____ starts expanding. The yolk sac's ____ circulation is responsible for the early uptake and transport of nutrients and oxygen. It is, however, soon replaced by the ____ circulation.	embryo proper allantois vitelline umbilical (allantoic)
The amnion and chorion are completely formed by day ___.	14
The amniotic sac largely occupies the central portion of the _____1______. However, a narrow portion of the __2__ lies ventro-laterally and to the right of the amniotic sac. The amnion thus lies against the __3__ dorsally, laterally on the left, dorso-laterally on the right, and ventrally (except for a narrow central area occupied by the __2__); the amnion and __3__ fuse to form __4__ in these areas.	1. fusiform chorionic sac 2. allantois 3. chorion 4. amniochorion
The allantoamnion is formed where the ____ abuts the ___. The amniochorion and allantoamnion are both vascularized by the ____ circulation; the amniochorion forms part of the ____ of the placenta.	amnion allantois umbilical Pars fetalis
Amniotic plaques, which develop as ____ proliferations with ____ tips, start appearing after from ____.	epithelial keratinized 3 months
The amniotic fluid is initially clear and colourless, but becomes yellowish later. At partus, the amniotic fluid volume ranges from ___ to ___ litres.	1 - 6
The allantois is seen evaginating on day ___ in the bovine and on day ___ in the sheep. It expands (causing regression of the yolk sac), filling the ____ and occupying both extremities of the chorionic sac by day ___ in the bovine and day ___ in the sheep.	21 18 exocoelom 35 28
The allantois is approximately T-shaped, once it and the amniotic sac are fully formed. The (horizontal) crossbar of the T is very long and runs the length of the __1__. The ends of the crossbar are dilated and fully occupy the extremities of the __1__. The central section of the crossbar is narrow and flattened; it lies between the __2__ and the __3__ on the right side (relative to the position of the embryo/fetus). The (vertical) shaft of the T connects the crossbar to the __4__ of the embryo/fetus. Since the crossbar lies to the right of the __2__, it is clear that the distal part of the shaft must curve dorsally to reach the __4__.	1. chorionic sac 2. amniotic sac 3. chorion 4. umbilicus
If one views a transverse section of the conceptus (at the level of the umbilicus) from caudal, the shaft of the T (now viewed side-on) is not straight, but actually___-shaped: the tip of the right arm joins to the cross-bar, while the tip of the left arm attaches to the fetus/embryo	J- or U
Allantochorion is formed wherever the ____ and ____ lie in apposition. Formation begins on day ___ in the bovine, and on day ___ in the sheep.	allantois chorion 33 30
The allantochorion is well vascularized by the ____ vessels; however, the tips of the ____ ____ are not vascularized and become necrotic.	umbilical chorionic sac
Hippomanes also occur in the ruminant ____ fluid; they are generally ____ in the bovine, ____ in the sheep and _____ in the goat.	allantoic greenish brownish dirty-white
At partus, the allantoic fluid volume is ____ litres in the bovine and ____ litres in the sheep.	3,5-12 0,7-1,1
In the ruminants, ____ nutrition occurs at numerous focal areas of attachment; these areas are known as ____. There are ____ placentomes in the bovine, ____ in the sheep and ____ in the goat.	hemotrophic placentomes 70-140 80-100 160-180
Each placentome has a fetal component, known as a ____, and a maternal component, known as a ____. The caruncles are ____, _____ proliferations of uterine subepithelial connective tissue. They are a permanent feature of the endometrium and are roughly arranged in two dorsal rows and two ventral rows.	cotyledon caruncle nodular non-glandular
In the bovine, the caruncles are ____ and ____ (i.e. attached to the endometrium by means of a short stalk) (see Fig. 26)	nodular pedunculated
In the sheep and goat, the caruncular surface is ____ and the caruncles resemble small cups (deep in the ____, shallow in the ____). In both species, the brim of the cup is folded inward to form a definite lip (see Figs. 28 and 30).	concave sheep goat
A cotyledon develops wherever the chorion makes contact with a __1__. Masses of ____2____ form at each contact site. The __2__ become enlarged and each develops a __________. Each focal mass of chorionic villi constitutes a cotyledon.	1. caruncle 2. chorionic villi vascular mesodermal core
Cotyledons develop on both the ____ and ____, but their number and position are determined by the ____. No villi ever develop on the necrotic tips of the chorionic sac.	allantochorion amniochorion caruncles
The chorionic villi are initially accommodated in corresponding depressions in the caruncle. However, as the villi grow and branch, the depressions deepen to form __1__ (the caruncular tissue between the deepening __1__ now constitutes maternal or caruncular villi). Simultaneously, the caruncle becomes enlarged and more vascular. The caruncles in the pregnant horn enlarge tremendously; the largest measure _3_ cm in the bovine, and _4_ cm in the sheep. The caruncles in the non-pregnant horn also enlarge, but to a lesser extent.	1. crypts 2. 14 x 5 cm 3. 3 x 3 cm
In the bovine, the cotyledons are ____; the villi are arranged ____ and project towards the ____ of the (nodular) caruncle. The edge of the cotyledon folds inwards, towards the ____ of the caruncle; the cotyledon thus surrounds or embraces the caruncle (see Fig. 26).	concave radially centre stalk
In the sheep and goat, the cotyledons are nodular and pedunculated (i.e. attached to the chorion by a short stalk); the villi are also arranged ____, but project towards the ____ of the (cup-shaped) caruncle. The brim of the caruncle folds inwards, towards the stalk of the cotyledon; the caruncle thus surrounds or embraces the cotyledon (see Figs. 28 and 30).	radially periphery
In the bovine, chorionic villi start forming on about day ___; by day ___ there is already significant interdigitation of fetal and maternal villi and microvilli. The villi are fully developed and attachment is complete by about day ___.	30 35 120
In the sheep, chorionic villi start forming on about day __ and are completely developed by day __.	30 78
In the bovine. The fetal and caruncular villi gradually become more branched and complex which greatly enhances their interdigitation. The epithelium covering the bases of the fetal villi is __1__, while that covering the tips is __2__; both cell types have microvilli. The microvilli of the __2__ cells interdigitate with microvilli in the depths of the caruncular crypts (i.e. on the bases of the caruncular villi). However, the cells covering the tips of the caruncular villi do not have microvilli (the microvilli of the __1__ cells therefore cannot interdigitate).	1. columnar 2. cuboidal
In the bovine. The columnar cells (base) of the fetal villi are responsible for ____ nutrition, while the cuboidal cells (tips) are responsible for ____ nutrition. Intra-epithelial capillaries are only found in the ____ epithelium (in other species, they also occur in the uterine epithelium).	histotrophic hemotrophic chorionic
In the sheep and goat, the epithelium covering the tips of the caruncular villi forms __1__. These are masses of cells that lose their __2__ where they lie in contact with each other; they appear as large, multinucleate cytoplasmic masses surrounded by an outer __2__. The presence of the __1__ creates the impression that the chorionic epithelium lies against the maternal connective tissue between these masses. However, the uterine epithelium covering the masses remains intact.	1. symplasma masses 2. plasmalemma
In the bovine, granular giant and binucleate cells from the chorionic epithelium migrate to the caruncular epithelium on about day __. These cells later migrate back to the chorionic epithelium as ____ ____ cells. The exact purpose of this migration is uncertain, but it may involve the transport of non-diffusable substances.	17 pycnotic agranular
From about the middle of the pregnancy, the tips of the ____ villi become eroded; this erosion also affects the capillaries and results in hemorrhage and blood pooling at the bases of the ____ villi. The red blood cells are then absorbed by the columnar chorionic epithelium as ____. After the cells have been digested, the ____ (from the maternal hemoglobin) is used in fetal ____.	caruncular fetal histotrophe iron hematopoiesis (production of all of the cellular components of blood and blood plasma)
Erosion of the caruncular villi tips occur regularly in the _____ and obviously facilitate ____ nutrition. In the _____, these hemorrhages only occur occasionally, and red blood cells may rather be supplied to the fetus by ____ (i.e. active migration of red blood cells from the capillaries).	sheep and goat histotrophic bovine diapedesis
The chorionic villi that initially developed in the paraplacental areas (i.e. the areas between the cotyledons) soon disappear. However, the epithelium in these areas continues to absorb ____ that accumulates between the ____ and ____. The uterine glands between the ____ are well developed and secrete large volumes. These secretions are augmented by uterine ____ epithelium, which appears to be sloughed and replaced at regular intervals.	histotrophe chorion endometrium caruncles paraplacental
In the bovine, adventitious caruncles may develop after day ____. The chorionic attachment to these caruncles is less firm than that of the permanent caruncles. The largest never exceed ± ___ cm in diameter and their importance is uncertain. Adventitious caruncles do not develop in the sheep or goat.	120 2,5
In the bovine, twins may share the same uterine horn, or may develop in separate horns. In either case, varying degrees of chorionic fusion can occur and may result in the formation of ____ between the two chorionic (umbilical) circulations; this, in turn, may result in blood cell ____ (individual having blood cells derived from a heterozygous twin, in addition to its own).	anastomoses (connection or opening between two things that are normally diverging or branching) chimerism
How does a Freemartin calf occur?	Blood cell chimerism is particularly significant when it involves heterosexual twins (i.e. male and female). The female fetus will thus have blood cells with XY chromosomes derived from the male in addition to her own blood cells with XX chromosomes. The Y-chromosomes suppress the development of the female genital system, resulting in a sterile heifer known as a freemartin. Freemartins develop in about 85 % of heterosexual twin pregnancies.
Describe the occurance of Freemartinism in sheep and goats.	In the sheep and goat, the chorionic sacs of twins and triplets always fuse and connections between the allantoic sacs are often seen. Chorionic vascular anastomosis and consequent freemartinism also occur in heterosexual twins/triplets, but much less frequently than in the bovine.
When compared to fetal body length at birth, the ruminant umbilical cord is the shortest of all the domestic mammals. In the bovine and sheep, it is ____ of body length, while in the goat, only ____. The two umbilical arteries are not spirally twisted and the two umbilical veins fuse before reaching the ____. Amniotic plaques are present and are particularly well developed. The umbilical cord has no ____ component as in the horse.	1/4 1/6 umbilicus allantoic
Classify the ruminant placenta.	1. chorioamniotic 2. chorioallantoic 3. adeciduate 4. cotyledonary 5. epitheliochorial